The following commit has been merged into the x86/urgent branch of tip:

Commit-ID: cdaa0a407f1acd3a44861e3aea6e3c7349e668f1 Gitweb: https://git.kernel.org/tip/cdaa0a407f1acd3a44861e3aea6e3c7349e668f1 Author: Tom Lendacky thomas.lendacky@amd.com AuthorDate: Tue, 23 Aug 2022 16:55:51 -05:00 Committer: Borislav Petkov bp@suse.de CommitterDate: Wed, 24 Aug 2022 09:54:32 +02:00

x86/sev: Don't use cc_platform_has() for early SEV-SNP calls

When running identity-mapped and depending on the kernel configuration, it is possible that the compiler uses jump tables when generating code for cc_platform_has().

This causes a boot failure because the jump table uses un-mapped kernel virtual addresses, not identity-mapped addresses. This has been seen with CONFIG_RETPOLINE=n.

Similar to sme_encrypt_kernel(), use an open-coded direct check for the status of SNP rather than trying to eliminate the jump table. This preserves any code optimization in cc_platform_has() that can be useful post boot. It also limits the changes to SEV-specific files so that future compiler features won't necessarily require possible build changes just because they are not compatible with running identity-mapped.

[ bp: Massage commit message. ]

Fixes: 5e5ccff60a29 ("x86/sev: Add helper for validating pages in early enc attribute changes") Reported-by: Sean Christopherson seanjc@google.com Suggested-by: Sean Christopherson seanjc@google.com Signed-off-by: Tom Lendacky thomas.lendacky@amd.com Signed-off-by: Borislav Petkov bp@suse.de Cc: stable@vger.kernel.org # 5.19.x Link: https://lore.kernel.org/all/YqfabnTRxFSM+LoX@google.com/ --- arch/x86/kernel/sev.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c index 63dc626..4f84c3f 100644 --- a/arch/x86/kernel/sev.c +++ b/arch/x86/kernel/sev.c @@ -701,7 +701,13 @@ e_term: void __init early_snp_set_memory_private(unsigned long vaddr, unsigned long paddr, unsigned int npages) { - if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) + /* + * This can be invoked in early boot while running identity mapped, so + * use an open coded check for SNP instead of using cc_platform_has(). + * This eliminates worries about jump tables or checking boot_cpu_data + * in the cc_platform_has() function. + */ + if (!(sev_status & MSR_AMD64_SEV_SNP_ENABLED)) return;

/* @@ -717,7 +723,13 @@ void __init early_snp_set_memory_private(unsigned long vaddr, unsigned long padd void __init early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr, unsigned int npages) { - if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) + /* + * This can be invoked in early boot while running identity mapped, so + * use an open coded check for SNP instead of using cc_platform_has(). + * This eliminates worries about jump tables or checking boot_cpu_data + * in the cc_platform_has() function. + */ + if (!(sev_status & MSR_AMD64_SEV_SNP_ENABLED)) return;

/* Invalidate the memory pages before they are marked shared in the RMP table. */