From: Nikunj A Dadhania <nikunj@amd.com>
To: <linux-kernel@vger.kernel.org>, <thomas.lendacky@amd.com>,
<bp@alien8.de>, <x86@kernel.org>, <kvm@vger.kernel.org>
Cc: <mingo@redhat.com>, <tglx@linutronix.de>,
<dave.hansen@linux.intel.com>, <pgonda@google.com>,
<seanjc@google.com>, <pbonzini@redhat.com>, <nikunj@amd.com>
Subject: [PATCH v8 11/16] x86/sev: Change TSC MSR behavior for Secure TSC enabled guests
Date: Thu, 15 Feb 2024 17:01:23 +0530 [thread overview]
Message-ID: <20240215113128.275608-12-nikunj@amd.com> (raw)
In-Reply-To: <20240215113128.275608-1-nikunj@amd.com>
Secure TSC enabled guests should not write MSR_IA32_TSC(10H) register
as the subsequent TSC value reads are undefined. MSR_IA32_TSC related
accesses should not exit to the hypervisor for such guests.
Accesses to MSR_IA32_TSC needs special handling in the #VC handler for
the guests with Secure TSC enabled. Writes to MSR_IA32_TSC should be
ignored, and reads of MSR_IA32_TSC should return the result of the
RDTSC instruction.
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Tested-by: Peter Gonda <pgonda@google.com>
---
arch/x86/kernel/sev.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 20a1e50b7638..64243c44a7d3 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -1279,6 +1279,30 @@ static enum es_result vc_handle_msr(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
/* Is it a WRMSR? */
exit_info_1 = (ctxt->insn.opcode.bytes[1] == 0x30) ? 1 : 0;
+ /*
+ * TSC related accesses should not exit to the hypervisor when a
+ * guest is executing with SecureTSC enabled, so special handling
+ * is required for accesses of MSR_IA32_TSC:
+ *
+ * Writes: Writing to MSR_IA32_TSC can cause subsequent reads
+ * of the TSC to return undefined values, so ignore all
+ * writes.
+ * Reads: Reads of MSR_IA32_TSC should return the current TSC
+ * value, use the value returned by RDTSC.
+ */
+ if (regs->cx == MSR_IA32_TSC && cpu_feature_enabled(X86_FEATURE_SNP_SECURE_TSC)) {
+ u64 tsc;
+
+ if (exit_info_1)
+ return ES_OK;
+
+ tsc = rdtsc();
+ regs->ax = UINT_MAX & tsc;
+ regs->dx = UINT_MAX & (tsc >> 32);
+
+ return ES_OK;
+ }
+
ghcb_set_rcx(ghcb, regs->cx);
if (exit_info_1) {
ghcb_set_rax(ghcb, regs->ax);
--
2.34.1
next prev parent reply other threads:[~2024-02-15 11:32 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-15 11:31 [PATCH v8 00/16] Add Secure TSC support for SNP guests Nikunj A Dadhania
2024-02-15 11:31 ` [PATCH v8 01/16] virt: sev-guest: Use AES GCM crypto library Nikunj A Dadhania
2024-02-27 18:25 ` Borislav Petkov
2024-02-15 11:31 ` [PATCH v8 02/16] virt: sev-guest: Replace dev_dbg with pr_debug Nikunj A Dadhania
2024-02-27 18:28 ` Borislav Petkov
2024-02-15 11:31 ` [PATCH v8 03/16] virt: sev-guest: Add SNP guest request structure Nikunj A Dadhania
2024-02-27 22:20 ` Tom Lendacky
2024-02-29 9:12 ` Nikunj A. Dadhania
2024-02-28 11:50 ` Borislav Petkov
2024-02-29 9:26 ` Nikunj A. Dadhania
2024-02-15 11:31 ` [PATCH v8 04/16] virt: sev-guest: Add vmpck_id to snp_guest_dev struct Nikunj A Dadhania
2024-04-09 10:23 ` Borislav Petkov
2024-04-16 5:57 ` Nikunj A. Dadhania
2024-04-16 9:06 ` Borislav Petkov
2024-04-17 4:18 ` Nikunj A. Dadhania
2024-02-15 11:31 ` [PATCH v8 05/16] x86/sev: Cache the secrets page address Nikunj A Dadhania
2024-04-16 14:45 ` Borislav Petkov
2024-04-17 5:27 ` Nikunj A. Dadhania
2024-04-17 7:59 ` Nikunj A. Dadhania
2024-02-15 11:31 ` [PATCH v8 06/16] virt: sev-guest: Move SNP Guest command mutex Nikunj A Dadhania
2024-04-22 13:00 ` Borislav Petkov
2024-04-23 4:22 ` Nikunj A. Dadhania
2024-04-23 10:28 ` Borislav Petkov
2024-04-23 10:42 ` Nikunj A. Dadhania
2024-04-23 11:21 ` Borislav Petkov
2024-02-15 11:31 ` [PATCH v8 07/16] x86/sev: Move and reorganize sev guest request api Nikunj A Dadhania
2024-04-22 13:14 ` Borislav Petkov
2024-04-23 4:26 ` Nikunj A. Dadhania
2024-04-23 13:22 ` Borislav Petkov
2024-02-15 11:31 ` [PATCH v8 08/16] x86/mm: Add generic guest initialization hook Nikunj A Dadhania
2024-04-22 13:20 ` Borislav Petkov
2024-04-23 4:34 ` Nikunj A. Dadhania
2024-02-15 11:31 ` [PATCH v8 09/16] x86/cpufeatures: Add synthetic Secure TSC bit Nikunj A Dadhania
2024-04-22 13:25 ` Borislav Petkov
2024-04-23 4:40 ` Nikunj A. Dadhania
2024-04-23 13:29 ` Borislav Petkov
2024-02-15 11:31 ` [PATCH v8 10/16] x86/sev: Add Secure TSC support for SNP guests Nikunj A Dadhania
2024-04-22 13:50 ` Borislav Petkov
2024-04-23 4:44 ` Nikunj A. Dadhania
2024-02-15 11:31 ` Nikunj A Dadhania [this message]
2024-02-15 11:31 ` [PATCH v8 12/16] x86/sev: Prevent RDTSC/RDTSCP interception for Secure TSC enabled guests Nikunj A Dadhania
2024-02-15 11:31 ` [PATCH v8 13/16] x86/kvmclock: Skip kvmclock when Secure TSC is available Nikunj A Dadhania
2024-02-15 11:31 ` [PATCH v8 14/16] x86/sev: Mark Secure TSC as reliable Nikunj A Dadhania
2024-02-15 11:31 ` [PATCH v8 15/16] x86/cpu/amd: Do not print FW_BUG for Secure TSC Nikunj A Dadhania
2024-02-15 11:31 ` [PATCH v8 16/16] x86/sev: Enable Secure TSC for SNP guests Nikunj A Dadhania
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