[PATCH v2 2/2] x86/sev-es: Only set x86_virt_bits to correct value

From: Adam Dunlap <acdunlap@google.com>
To: linux-kernel@vger.kernel.org, x86@kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Sean Christopherson <seanjc@google.com>,
	Kim Phillips <kim.phillips@amd.com>,
	Juergen Gross <jgross@suse.com>, Ashok Raj <ashok.raj@intel.com>,
	Adam Dunlap <acdunlap@google.com>, Joerg Roedel <jroedel@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>,
	David Hildenbrand <david@redhat.com>,
	Mike Rapoport <rppt@kernel.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Nikunj A Dadhania <nikunj@amd.com>,
	Dionna Glaze <dionnaglaze@google.com>,
	Peter Gonda <pgonda@google.com>,
	David Rientjes <rientjes@google.com>,
	Khalid ElMously <khalid.elmously@canonical.com>,
	Jacob Xu <jacobhxu@google.com>
Subject: [PATCH v2 2/2] x86/sev-es: Only set x86_virt_bits to correct value
Date: Mon, 11 Sep 2023 17:27:03 -0700	[thread overview]
Message-ID: <20230912002703.3924521-3-acdunlap@google.com> (raw)
In-Reply-To: <20230912002703.3924521-1-acdunlap@google.com>

Instead of setting x86_virt_bits to a possibly-correct value and then
correcting it later, do all the necessary checks before setting it.

At this point, the #VC handler references boot_cpu_data.x86_virt_bits,
and in the previous version, it would be triggered by the cpuids between
the point at which it is set to 48 and when it is set to the correct
value.

Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Adam Dunlap <acdunlap@google.com>
---
 arch/x86/kernel/cpu/common.c | 37 +++++++++++++++++++++---------------
 1 file changed, 22 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 52683fddafaf..23888d3da16f 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1099,17 +1099,32 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
 void get_cpu_address_sizes(struct cpuinfo_x86 *c)
 {
 	u32 eax, ebx, ecx, edx;
+	bool vp_bits_from_cpuid = true;
 
-	if (c->extended_cpuid_level >= 0x80000008) {
+	if (!cpu_has(c, X86_FEATURE_CPUID) ||
+	    (c->extended_cpuid_level < 0x80000008))
+		vp_bits_from_cpuid = false;
+
+	if (vp_bits_from_cpuid) {
 		cpuid(0x80000008, &eax, &ebx, &ecx, &edx);
 
 		c->x86_virt_bits = (eax >> 8) & 0xff;
 		c->x86_phys_bits = eax & 0xff;
+	} else {
+		if (IS_ENABLED(CONFIG_X86_64)) {
+			c->x86_clflush_size = 64;
+			c->x86_phys_bits = 36;
+			c->x86_virt_bits = 48;
+		} else {
+			c->x86_clflush_size = 32;
+			c->x86_virt_bits = 32;
+			c->x86_phys_bits = 32;
+
+			if (cpu_has(c, X86_FEATURE_PAE) ||
+			    cpu_has(c, X86_FEATURE_PSE36))
+				c->x86_phys_bits = 36;
+		}
 	}
-#ifdef CONFIG_X86_32
-	else if (cpu_has(c, X86_FEATURE_PAE) || cpu_has(c, X86_FEATURE_PSE36))
-		c->x86_phys_bits = 36;
-#endif
 	c->x86_cache_bits = c->x86_phys_bits;
 }
 
@@ -1539,15 +1554,6 @@ static void __init cpu_parse_early_param(void)
  */
 static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 {
-#ifdef CONFIG_X86_64
-	c->x86_clflush_size = 64;
-	c->x86_phys_bits = 36;
-	c->x86_virt_bits = 48;
-#else
-	c->x86_clflush_size = 32;
-	c->x86_phys_bits = 32;
-	c->x86_virt_bits = 32;
-#endif
 	c->x86_cache_alignment = c->x86_clflush_size;
 
 	memset(&c->x86_capability, 0, sizeof(c->x86_capability));
@@ -1561,7 +1567,6 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 		cpu_detect(c);
 		get_cpu_vendor(c);
 		get_cpu_cap(c);
-		get_cpu_address_sizes(c);
 		setup_force_cpu_cap(X86_FEATURE_CPUID);
 		cpu_parse_early_param();
 
@@ -1577,6 +1582,8 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 		setup_clear_cpu_cap(X86_FEATURE_CPUID);
 	}
 
+	get_cpu_address_sizes(c);
+
 	setup_force_cpu_cap(X86_FEATURE_ALWAYS);
 
 	cpu_set_bug_bits(c);
-- 
2.42.0.283.g2d96d420d3-goog

