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authorTom Lendacky <thomas.lendacky@amd.com>2022-08-23 16:55:51 -0500
committerBorislav Petkov <bp@suse.de>2022-08-24 09:54:32 +0200
commitcdaa0a407f1acd3a44861e3aea6e3c7349e668f1 (patch)
tree2d6f7614d0bd40804ffe6ffa2b860774f13781ac /arch
parent4b1c742407571eff58b6de9881889f7ca7c4b4dc (diff)
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/
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/sev.c16
1 files changed, 14 insertions, 2 deletions
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 63dc626627a0..4f84c3f11af5 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. */