From: Volodymyr Babchuk Volodymyr_Babchuk@epam.com
Linux does not write into cmd-db region. This region of memory is write protected by XPU. XPU may sometime falsely detect clean cache eviction as "write" into the write protected region leading to secure interrupt which causes an endless loop somewhere in Trust Zone.
The only reason it is working right now is because Qualcomm Hypervisor maps the same region as Non-Cacheable memory in Stage 2 translation tables. The issue manifests if we want to use another hypervisor (like Xen or KVM), which does not know anything about those specific mappings.
Changing the mapping of cmd-db memory from MEMREMAP_WB to MEMREMAP_WT/WC removes dependency on correct mappings in Stage 2 tables. This patch fixes the issue by updating the mapping to MEMREMAP_WC.
I tested this on SA8155P with Xen.
Fixes: 312416d9171a ("drivers: qcom: add command DB driver") Cc: stable@vger.kernel.org # 5.4+ Signed-off-by: Volodymyr Babchuk volodymyr_babchuk@epam.com Tested-by: Nikita Travkin nikita@trvn.ru # sc7180 WoA in EL2 Signed-off-by: Maulik Shah quic_mkshah@quicinc.com --- Changes in v2: - Use MEMREMAP_WC instead of MEMREMAP_WT - Update commit message from comments in v1 - Add Fixes tag and Cc to stable - Link to v1: https://lore.kernel.org/lkml/20240327200917.2576034-1-volodymyr_babchuk@epam... --- drivers/soc/qcom/cmd-db.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/soc/qcom/cmd-db.c b/drivers/soc/qcom/cmd-db.c index d84572662017..ae66c2623d25 100644 --- a/drivers/soc/qcom/cmd-db.c +++ b/drivers/soc/qcom/cmd-db.c @@ -349,7 +349,7 @@ static int cmd_db_dev_probe(struct platform_device *pdev) return -EINVAL; }
- cmd_db_header = memremap(rmem->base, rmem->size, MEMREMAP_WB); + cmd_db_header = memremap(rmem->base, rmem->size, MEMREMAP_WC); if (!cmd_db_header) { ret = -ENOMEM; cmd_db_header = NULL;
--- base-commit: 797012914d2d031430268fe512af0ccd7d8e46ef change-id: 20240718-cmd_db_uncached-e896da5c5296
Best regards,
On Thu, Jul 18, 2024 at 11:33:23AM +0530, Maulik Shah wrote:
From: Volodymyr Babchuk Volodymyr_Babchuk@epam.com
Linux does not write into cmd-db region. This region of memory is write protected by XPU. XPU may sometime falsely detect clean cache eviction as "write" into the write protected region leading to secure interrupt which causes an endless loop somewhere in Trust Zone.
The only reason it is working right now is because Qualcomm Hypervisor maps the same region as Non-Cacheable memory in Stage 2 translation tables. The issue manifests if we want to use another hypervisor (like Xen or KVM), which does not know anything about those specific mappings.
Changing the mapping of cmd-db memory from MEMREMAP_WB to MEMREMAP_WT/WC removes dependency on correct mappings in Stage 2 tables. This patch fixes the issue by updating the mapping to MEMREMAP_WC.
I tested this on SA8155P with Xen.
Fixes: 312416d9171a ("drivers: qcom: add command DB driver") Cc: stable@vger.kernel.org # 5.4+ Signed-off-by: Volodymyr Babchuk volodymyr_babchuk@epam.com Tested-by: Nikita Travkin nikita@trvn.ru # sc7180 WoA in EL2 Signed-off-by: Maulik Shah quic_mkshah@quicinc.com
Changes in v2:
- Use MEMREMAP_WC instead of MEMREMAP_WT
- Update commit message from comments in v1
- Add Fixes tag and Cc to stable
- Link to v1: https://lore.kernel.org/lkml/20240327200917.2576034-1-volodymyr_babchuk@epam...
drivers/soc/qcom/cmd-db.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/soc/qcom/cmd-db.c b/drivers/soc/qcom/cmd-db.c index d84572662017..ae66c2623d25 100644 --- a/drivers/soc/qcom/cmd-db.c +++ b/drivers/soc/qcom/cmd-db.c @@ -349,7 +349,7 @@ static int cmd_db_dev_probe(struct platform_device *pdev) return -EINVAL; }
- cmd_db_header = memremap(rmem->base, rmem->size, MEMREMAP_WB);
- cmd_db_header = memremap(rmem->base, rmem->size, MEMREMAP_WC); if (!cmd_db_header) { ret = -ENOMEM; cmd_db_header = NULL;
Thanks Maulik for sharing the patch. It works as expected. Feel free to use
Tested-by: Pavankumar Kondeti quic_pkondeti@quicinc.com
Thanks, Pavan
Hi Pavan,
Thanks Maulik for sharing the patch. It works as expected. Feel free to use
Can I ask how you're testing this?
Kind regards,
Tested-by: Pavankumar Kondeti quic_pkondeti@quicinc.com
Thanks, Pavan
On Thu, Jul 18, 2024 at 09:42:27AM +0200, Caleb Connolly wrote:
Hi Pavan,
Thanks Maulik for sharing the patch. It works as expected. Feel free to use
Can I ask how you're testing this?
Kind regards,
Tested-by: Pavankumar Kondeti quic_pkondeti@quicinc.com
The QCM6490 RB3 board boots from upstream kernel. As part of releases here [1] we plan to support booting Linux in EL2. Currently, I have an internal board/build with firmware allowing this already. I have boot tested Maulik's patch (and as well v1 patch). The targets gets reset early in the boot up w/o this patch and I could boot w/ this patch.
Thanks, Pavan
On 18/07/2024 09:55, Pavan Kondeti wrote:
On Thu, Jul 18, 2024 at 09:42:27AM +0200, Caleb Connolly wrote:
Hi Pavan,
Thanks Maulik for sharing the patch. It works as expected. Feel free to use
Can I ask how you're testing this?
Kind regards,
Tested-by: Pavankumar Kondeti quic_pkondeti@quicinc.com
The QCM6490 RB3 board boots from upstream kernel. As part of releases here [1] we plan to support booting Linux in EL2. Currently, I have an internal board/build with firmware allowing this already. I have boot tested Maulik's patch (and as well v1 patch). The targets gets reset early in the boot up w/o this patch and I could boot w/ this patch.
Ahh awesome! Thanks for the info :)
Thanks, Pavan
On 18/07/2024 08:03, Maulik Shah wrote:
From: Volodymyr Babchuk Volodymyr_Babchuk@epam.com
Linux does not write into cmd-db region. This region of memory is write protected by XPU. XPU may sometime falsely detect clean cache eviction as "write" into the write protected region leading to secure interrupt which causes an endless loop somewhere in Trust Zone.
The only reason it is working right now is because Qualcomm Hypervisor maps the same region as Non-Cacheable memory in Stage 2 translation tables. The issue manifests if we want to use another hypervisor (like Xen or KVM), which does not know anything about those specific mappings.
Changing the mapping of cmd-db memory from MEMREMAP_WB to MEMREMAP_WT/WC removes dependency on correct mappings in Stage 2 tables. This patch fixes the issue by updating the mapping to MEMREMAP_WC.
I tested this on SA8155P with Xen.
Fixes: 312416d9171a ("drivers: qcom: add command DB driver") Cc: stable@vger.kernel.org # 5.4+ Signed-off-by: Volodymyr Babchuk volodymyr_babchuk@epam.com Tested-by: Nikita Travkin nikita@trvn.ru # sc7180 WoA in EL2 Signed-off-by: Maulik Shah quic_mkshah@quicinc.com
Reviewed-by: Caleb Connolly caleb.connolly@linaro.org
Changes in v2:
- Use MEMREMAP_WC instead of MEMREMAP_WT
- Update commit message from comments in v1
- Add Fixes tag and Cc to stable
- Link to v1: https://lore.kernel.org/lkml/20240327200917.2576034-1-volodymyr_babchuk@epam...
drivers/soc/qcom/cmd-db.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/soc/qcom/cmd-db.c b/drivers/soc/qcom/cmd-db.c index d84572662017..ae66c2623d25 100644 --- a/drivers/soc/qcom/cmd-db.c +++ b/drivers/soc/qcom/cmd-db.c @@ -349,7 +349,7 @@ static int cmd_db_dev_probe(struct platform_device *pdev) return -EINVAL; }
- cmd_db_header = memremap(rmem->base, rmem->size, MEMREMAP_WB);
- cmd_db_header = memremap(rmem->base, rmem->size, MEMREMAP_WC); if (!cmd_db_header) { ret = -ENOMEM; cmd_db_header = NULL;
base-commit: 797012914d2d031430268fe512af0ccd7d8e46ef change-id: 20240718-cmd_db_uncached-e896da5c5296
Best regards,
Hi Bjorn,
On Thu, Jul 18, 2024 at 09:41:34AM +0200, Caleb Connolly wrote:
On 18/07/2024 08:03, Maulik Shah wrote:
From: Volodymyr Babchuk Volodymyr_Babchuk@epam.com
Linux does not write into cmd-db region. This region of memory is write protected by XPU. XPU may sometime falsely detect clean cache eviction as "write" into the write protected region leading to secure interrupt which causes an endless loop somewhere in Trust Zone.
The only reason it is working right now is because Qualcomm Hypervisor maps the same region as Non-Cacheable memory in Stage 2 translation tables. The issue manifests if we want to use another hypervisor (like Xen or KVM), which does not know anything about those specific mappings.
Changing the mapping of cmd-db memory from MEMREMAP_WB to MEMREMAP_WT/WC removes dependency on correct mappings in Stage 2 tables. This patch fixes the issue by updating the mapping to MEMREMAP_WC.
I tested this on SA8155P with Xen.
Fixes: 312416d9171a ("drivers: qcom: add command DB driver") Cc: stable@vger.kernel.org # 5.4+ Signed-off-by: Volodymyr Babchuk volodymyr_babchuk@epam.com Tested-by: Nikita Travkin nikita@trvn.ru # sc7180 WoA in EL2 Signed-off-by: Maulik Shah quic_mkshah@quicinc.com
Reviewed-by: Caleb Connolly caleb.connolly@linaro.org
Is it possible to include it in v6.11-rc?
Thanks, Pavan
On Thu, 18 Jul 2024 11:33:23 +0530, Maulik Shah wrote:
Linux does not write into cmd-db region. This region of memory is write protected by XPU. XPU may sometime falsely detect clean cache eviction as "write" into the write protected region leading to secure interrupt which causes an endless loop somewhere in Trust Zone.
The only reason it is working right now is because Qualcomm Hypervisor maps the same region as Non-Cacheable memory in Stage 2 translation tables. The issue manifests if we want to use another hypervisor (like Xen or KVM), which does not know anything about those specific mappings.
[...]
Applied, thanks!
[1/1] soc: qcom: cmd-db: Map shared memory as WC, not WB commit: f9bb896eab221618927ae6a2f1d566567999839d
Best regards,
linux-stable-mirror@lists.linaro.org
-
Bjorn Andersson -
Caleb Connolly -
Maulik Shah -
Pavan Kondeti