From: Long Li longli@microsoft.com
Interrupt and monitor pages should be in Hyper-V page size (4k bytes). This can be different to the system page size.
Cc: stable@vger.kernel.org Fixes: 95096f2fbd10 ("uio-hv-generic: new userspace i/o driver for VMBus") Signed-off-by: Long Li longli@microsoft.com --- drivers/uio/uio_hv_generic.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c index 1b19b5647495..08385b04c4ab 100644 --- a/drivers/uio/uio_hv_generic.c +++ b/drivers/uio/uio_hv_generic.c @@ -287,13 +287,13 @@ hv_uio_probe(struct hv_device *dev, pdata->info.mem[INT_PAGE_MAP].name = "int_page"; pdata->info.mem[INT_PAGE_MAP].addr = (uintptr_t)vmbus_connection.int_page; - pdata->info.mem[INT_PAGE_MAP].size = PAGE_SIZE; + pdata->info.mem[INT_PAGE_MAP].size = HV_HYP_PAGE_SIZE; pdata->info.mem[INT_PAGE_MAP].memtype = UIO_MEM_LOGICAL;
pdata->info.mem[MON_PAGE_MAP].name = "monitor_page"; pdata->info.mem[MON_PAGE_MAP].addr = (uintptr_t)vmbus_connection.monitor_pages[1]; - pdata->info.mem[MON_PAGE_MAP].size = PAGE_SIZE; + pdata->info.mem[MON_PAGE_MAP].size = HV_HYP_PAGE_SIZE; pdata->info.mem[MON_PAGE_MAP].memtype = UIO_MEM_LOGICAL;
if (channel->device_id == HV_NIC) {
From: longli@linuxonhyperv.com longli@linuxonhyperv.com
Interrupt and monitor pages should be in Hyper-V page size (4k bytes). This can be different to the system page size.
I'm curious about this change. Since Patch 1 of the series changes the allocations to be the full PAGE_SIZE, what does it mean to set the mapping size to less than a full page (in the case PAGE_SIZE > HV_HYP_PAGE_SIZE)? mmap can only map full PAGE_SIZE pages, so uio_mmap() rounds up the INT_PAGE_MAP and MON_PAGE_MAP sizes to PAGE_SIZE when checking the validity of the mmap parameters.
The changes in this patch do ensure that the INT_PAGE_MAP and MON_PAGE_MAP "maps" entries in sysfs always show the size as 4096 even if the full PAGE_SIZE is actually mapped, but I'm not sure if that difference is good or bad.
Michael
Cc: stable@vger.kernel.org Fixes: 95096f2fbd10 ("uio-hv-generic: new userspace i/o driver for VMBus") Signed-off-by: Long Li longli@microsoft.com
drivers/uio/uio_hv_generic.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c index 1b19b5647495..08385b04c4ab 100644 --- a/drivers/uio/uio_hv_generic.c +++ b/drivers/uio/uio_hv_generic.c @@ -287,13 +287,13 @@ hv_uio_probe(struct hv_device *dev, pdata->info.mem[INT_PAGE_MAP].name = "int_page"; pdata->info.mem[INT_PAGE_MAP].addr = (uintptr_t)vmbus_connection.int_page;
- pdata->info.mem[INT_PAGE_MAP].size = PAGE_SIZE;
pdata->info.mem[INT_PAGE_MAP].size = HV_HYP_PAGE_SIZE; pdata->info.mem[INT_PAGE_MAP].memtype = UIO_MEM_LOGICAL;
pdata->info.mem[MON_PAGE_MAP].name = "monitor_page"; pdata->info.mem[MON_PAGE_MAP].addr = (uintptr_t)vmbus_connection.monitor_pages[1];
- pdata->info.mem[MON_PAGE_MAP].size = PAGE_SIZE;
pdata->info.mem[MON_PAGE_MAP].size = HV_HYP_PAGE_SIZE; pdata->info.mem[MON_PAGE_MAP].memtype = UIO_MEM_LOGICAL;
if (channel->device_id == HV_NIC) {
-- 2.34.1
Subject: [EXTERNAL] RE: [PATCH 2/2] uio_hv_generic: Use correct size for interrupt and monitor pages
From: longli@linuxonhyperv.com longli@linuxonhyperv.com
Interrupt and monitor pages should be in Hyper-V page size (4k bytes). This can be different to the system page size.
I'm curious about this change. Since Patch 1 of the series changes the allocations to be the full PAGE_SIZE, what does it mean to set the mapping size to less than a full page (in the case PAGE_SIZE > HV_HYP_PAGE_SIZE)? mmap can only map full PAGE_SIZE pages, so uio_mmap() rounds up the INT_PAGE_MAP and MON_PAGE_MAP sizes to PAGE_SIZE when checking the validity of the mmap parameters.
The changes in this patch do ensure that the INT_PAGE_MAP and MON_PAGE_MAP "maps" entries in sysfs always show the size as 4096 even if the full PAGE_SIZE is actually mapped, but I'm not sure if that difference is good or bad.
Kernel needs to tell the user-mode the correct length of the map. In this case, 4096 bytes are usable data regardless of what is actual mapped as long as it's >4096.
The DPDK vmbus driver uses this length to setup checks for accessing the page.
Long
Michael
Cc: stable@vger.kernel.org Fixes: 95096f2fbd10 ("uio-hv-generic: new userspace i/o driver for VMBus") Signed-off-by: Long Li longli@microsoft.com
drivers/uio/uio_hv_generic.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c index 1b19b5647495..08385b04c4ab 100644 --- a/drivers/uio/uio_hv_generic.c +++ b/drivers/uio/uio_hv_generic.c @@ -287,13 +287,13 @@ hv_uio_probe(struct hv_device *dev, pdata->info.mem[INT_PAGE_MAP].name = "int_page"; pdata->info.mem[INT_PAGE_MAP].addr = (uintptr_t)vmbus_connection.int_page;
- pdata->info.mem[INT_PAGE_MAP].size = PAGE_SIZE;
pdata->info.mem[INT_PAGE_MAP].size = HV_HYP_PAGE_SIZE; pdata->info.mem[INT_PAGE_MAP].memtype = UIO_MEM_LOGICAL;
pdata->info.mem[MON_PAGE_MAP].name = "monitor_page"; pdata->info.mem[MON_PAGE_MAP].addr = (uintptr_t)vmbus_connection.monitor_pages[1];
- pdata->info.mem[MON_PAGE_MAP].size = PAGE_SIZE;
pdata->info.mem[MON_PAGE_MAP].size = HV_HYP_PAGE_SIZE; pdata->info.mem[MON_PAGE_MAP].memtype = UIO_MEM_LOGICAL;
if (channel->device_id == HV_NIC) {
-- 2.34.1
From: Long Li longli@microsoft.com Sent: Wednesday, April 23, 2025 11:49 AM
Interrupt and monitor pages should be in Hyper-V page size (4k bytes). This can be different to the system page size.
I'm curious about this change. Since Patch 1 of the series changes the allocations to be the full PAGE_SIZE, what does it mean to set the mapping size to less than a full page (in the case PAGE_SIZE > HV_HYP_PAGE_SIZE)? mmap can only map full PAGE_SIZE pages, so uio_mmap() rounds up the INT_PAGE_MAP and MON_PAGE_MAP sizes to PAGE_SIZE when checking the validity of the mmap parameters.
The changes in this patch do ensure that the INT_PAGE_MAP and MON_PAGE_MAP "maps" entries in sysfs always show the size as 4096 even if the full PAGE_SIZE is actually mapped, but I'm not sure if that difference is good or bad.
Kernel needs to tell the user-mode the correct length of the map. In this case, 4096 bytes are usable data regardless of what is actual mapped as long as it's >4096.
The DPDK vmbus driver uses this length to setup checks for accessing the page.
OK, so the "maps" entry needs to show a size of 4096 so the DPDK VMBus driver does the right thing.
At a minimum, mention in the commit message that the reason for the change is to always show 4096 as the size of the "maps" entries, even if PAGE_SIZE and the actual mapped area is larger. Perhaps also mention that the DPDK VMBus driver is one known consumer of that detail.
Michael
linux-stable-mirror@lists.linaro.org
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Michael Kelley