kvm.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Nikunj A Dadhania <nikunj@amd.com>
To: <linux-kernel@vger.kernel.org>, <thomas.lendacky@amd.com>,
	<x86@kernel.org>, <kvm@vger.kernel.org>
Cc: <bp@alien8.de>, <mingo@redhat.com>, <tglx@linutronix.de>,
	<dave.hansen@linux.intel.com>, <dionnaglaze@google.com>,
	<pgonda@google.com>, <seanjc@google.com>, <pbonzini@redhat.com>,
	<nikunj@amd.com>
Subject: [PATCH v7 11/16] x86/sev: Change TSC MSR behavior for Secure TSC enabled guests
Date: Wed, 20 Dec 2023 20:43:53 +0530	[thread overview]
Message-ID: <20231220151358.2147066-12-nikunj@amd.com> (raw)
In-Reply-To: <20231220151358.2147066-1-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 1d6200b57643..393d3be13934 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -1280,6 +1280,30 @@ 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


  parent reply	other threads:[~2023-12-20 15:15 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-12-20 15:13 [PATCH v7 00/16] Add Secure TSC support for SNP guests Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 01/16] virt: sev-guest: Use AES GCM crypto library Nikunj A Dadhania
2024-01-25 10:36   ` Borislav Petkov
2024-01-27  3:54     ` Nikunj A. Dadhania
2023-12-20 15:13 ` [PATCH v7 02/16] virt: sev-guest: Replace dev_dbg with pr_debug Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 03/16] virt: sev-guest: Add SNP guest request structure Nikunj A Dadhania
2024-01-25 11:59   ` Borislav Petkov
2024-01-27  4:01     ` Nikunj A. Dadhania
2024-01-31 13:58     ` Nikunj A. Dadhania
2024-02-01 10:29       ` Borislav Petkov
2024-02-01 11:10         ` Nikunj A. Dadhania
2024-02-01 14:07           ` Borislav Petkov
2024-02-02  3:50             ` Nikunj A. Dadhania
2024-02-02 16:14               ` Borislav Petkov
2024-02-05  9:23                 ` Nikunj A. Dadhania
2024-02-06 10:04                   ` Borislav Petkov
2024-01-26 21:16   ` Tom Lendacky
2024-01-27  4:05     ` Nikunj A. Dadhania
2023-12-20 15:13 ` [PATCH v7 04/16] virt: sev-guest: Add vmpck_id to snp_guest_dev struct Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 05/16] x86/sev: Cache the secrets page address Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 06/16] virt: sev-guest: Move SNP Guest command mutex Nikunj A Dadhania
2024-01-26 22:11   ` Tom Lendacky
2024-01-27  4:06     ` Nikunj A. Dadhania
2023-12-20 15:13 ` [PATCH v7 07/16] x86/sev: Move and reorganize sev guest request api Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 08/16] x86/mm: Add generic guest initialization hook Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 09/16] x86/cpufeatures: Add synthetic Secure TSC bit Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 10/16] x86/sev: Add Secure TSC support for SNP guests Nikunj A Dadhania
2024-02-01 15:46   ` Paolo Bonzini
2024-02-01 15:48     ` Paolo Bonzini
2023-12-20 15:13 ` Nikunj A Dadhania [this message]
2023-12-20 15:13 ` [PATCH v7 12/16] x86/sev: Prevent RDTSC/RDTSCP interception for Secure TSC enabled guests Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 13/16] x86/kvmclock: Skip kvmclock when Secure TSC is available Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 14/16] x86/sev: Mark Secure TSC as reliable Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 15/16] x86/cpu/amd: Do not print FW_BUG for Secure TSC Nikunj A Dadhania
2023-12-20 15:13 ` [PATCH v7 16/16] x86/sev: Enable Secure TSC for SNP guests Nikunj A Dadhania
2024-01-25  6:08 ` [PATCH v7 00/16] Add Secure TSC support " Nikunj A. Dadhania
2024-01-26  1:00   ` Dionna Amalie Glaze
2024-01-27  4:10     ` Nikunj A. Dadhania

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20231220151358.2147066-12-nikunj@amd.com \
    --to=nikunj@amd.com \
    --cc=bp@alien8.de \
    --cc=dave.hansen@linux.intel.com \
    --cc=dionnaglaze@google.com \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=pbonzini@redhat.com \
    --cc=pgonda@google.com \
    --cc=seanjc@google.com \
    --cc=tglx@linutronix.de \
    --cc=thomas.lendacky@amd.com \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).