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Subject[PATCH 21/62] x86/sev-es: Add CPUID handling to #VC handler
Date
From: Tom Lendacky <thomas.lendacky@amd.com>

Handle #VC exceptions caused by CPUID instructions. These happen in
early boot code when the KASLR code checks for RDTSC.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
[ jroedel@suse.de: Adapt to #VC handling framework ]
Co-developed-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
arch/x86/boot/compressed/sev-es.c | 4 ++++
arch/x86/kernel/sev-es-shared.c | 34 +++++++++++++++++++++++++++++++
2 files changed, 38 insertions(+)

diff --git a/arch/x86/boot/compressed/sev-es.c b/arch/x86/boot/compressed/sev-es.c
index b2a2d068dc12..270a23c05f53 100644
--- a/arch/x86/boot/compressed/sev-es.c
+++ b/arch/x86/boot/compressed/sev-es.c
@@ -10,6 +10,7 @@
#include <asm/sev-es.h>
#include <asm/trap_defs.h>
#include <asm/msr-index.h>
+#include <asm/fpu/xcr.h>
#include <asm/ptrace.h>
#include <asm/svm.h>

@@ -117,6 +118,9 @@ void boot_vc_handler(struct pt_regs *regs)
case SVM_EXIT_IOIO:
result = handle_ioio(boot_ghcb, &ctxt);
break;
+ case SVM_EXIT_CPUID:
+ result = handle_cpuid(boot_ghcb, &ctxt);
+ break;
default:
result = ES_UNSUPPORTED;
break;
diff --git a/arch/x86/kernel/sev-es-shared.c b/arch/x86/kernel/sev-es-shared.c
index bd21a79da084..0f422e3b2077 100644
--- a/arch/x86/kernel/sev-es-shared.c
+++ b/arch/x86/kernel/sev-es-shared.c
@@ -449,3 +449,37 @@ static enum es_result handle_ioio(struct ghcb *ghcb, struct es_em_ctxt *ctxt)

return ret;
}
+
+static enum es_result handle_cpuid(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
+{
+ struct pt_regs *regs = ctxt->regs;
+ u32 cr4 = native_read_cr4();
+ enum es_result ret;
+
+ ghcb_set_rax(ghcb, regs->ax);
+ ghcb_set_rcx(ghcb, regs->cx);
+
+ if (cr4 & X86_CR4_OSXSAVE)
+ /* Safe to read xcr0 */
+ ghcb_set_xcr0(ghcb, xgetbv(XCR_XFEATURE_ENABLED_MASK));
+ else
+ /* xgetbv will cause #GP - use reset value for xcr0 */
+ ghcb_set_xcr0(ghcb, 1);
+
+ ret = ghcb_hv_call(ghcb, ctxt, SVM_EXIT_CPUID, 0, 0);
+ if (ret != ES_OK)
+ return ret;
+
+ if (!(ghcb_is_valid_rax(ghcb) &&
+ ghcb_is_valid_rbx(ghcb) &&
+ ghcb_is_valid_rcx(ghcb) &&
+ ghcb_is_valid_rdx(ghcb)))
+ return ES_VMM_ERROR;
+
+ regs->ax = ghcb->save.rax;
+ regs->bx = ghcb->save.rbx;
+ regs->cx = ghcb->save.rcx;
+ regs->dx = ghcb->save.rdx;
+
+ return ES_OK;
+}
--
2.17.1
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