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From: Alexandru Elisei <alexandru.elisei@arm.com>
To: maz@kernel.org, linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu
Subject: [PATCH 1/2] KVM: arm64: Don't print warning when trapping SPE registers
Date: Fri,  9 Apr 2021 16:21:53 +0100	[thread overview]
Message-ID: <20210409152154.198566-2-alexandru.elisei@arm.com> (raw)
In-Reply-To: <20210409152154.198566-1-alexandru.elisei@arm.com>

KVM sets up MDCR_EL2 to trap accesses to the SPE buffer and sampling
control registers and it relies on the fact that KVM injects an undefined
exception for unknown registers. This mechanism of injecting undefined
exceptions also prints a warning message for the host kernel; for example,
when a guest tries to access PMSIDR_EL1:

[    2.691830] kvm [142]: Unsupported guest sys_reg access at: 80009e78 [800003c5]
[    2.691830]  { Op0( 3), Op1( 0), CRn( 9), CRm( 9), Op2( 7), func_read },

This is unnecessary, because KVM has explicitly configured trapping of
those registers and is well aware of their existence. Prevent the warning
by adding the SPE registers to the list of registers that KVM emulates.
The access function will inject the undefined exception.

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
---
 arch/arm64/include/asm/sysreg.h |  2 ++
 arch/arm64/kvm/sys_regs.c       | 13 +++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index d4a5fca984c3..43bca834c477 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -283,6 +283,8 @@
 #define SYS_PMSIRR_EL1_INTERVAL_MASK	0xffffffUL
 
 /* Filtering controls */
+#define SYS_PMSNEVFR_EL1		sys_reg(3, 0, 9, 9, 1)
+
 #define SYS_PMSFCR_EL1			sys_reg(3, 0, 9, 9, 4)
 #define SYS_PMSFCR_EL1_FE_SHIFT		0
 #define SYS_PMSFCR_EL1_FT_SHIFT		1
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 4f2f1e3145de..402cd11aa4fc 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1501,6 +1501,19 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
 	{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },
 
+	{ SYS_DESC(SYS_PMSCR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMSNEVFR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMSICR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMSIRR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMSFCR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMSEVFR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMSLATFR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMSIDR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMBLIMITR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMBPTR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMBSR_EL1), undef_access },
+	/* PMBIDR_EL1 is not trapped */
+
 	{ PMU_SYS_REG(SYS_PMINTENSET_EL1),
 	  .access = access_pminten, .reg = PMINTENSET_EL1 },
 	{ PMU_SYS_REG(SYS_PMINTENCLR_EL1),
-- 
2.31.1

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

WARNING: multiple messages have this Message-ID (diff)
From: Alexandru Elisei <alexandru.elisei@arm.com>
To: maz@kernel.org, linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu
Cc: james.morse@arm.com, julien.thierry.kdev@gmail.com,
	suzuki.poulose@arm.com
Subject: [PATCH 1/2] KVM: arm64: Don't print warning when trapping SPE registers
Date: Fri,  9 Apr 2021 16:21:53 +0100	[thread overview]
Message-ID: <20210409152154.198566-2-alexandru.elisei@arm.com> (raw)
In-Reply-To: <20210409152154.198566-1-alexandru.elisei@arm.com>

KVM sets up MDCR_EL2 to trap accesses to the SPE buffer and sampling
control registers and it relies on the fact that KVM injects an undefined
exception for unknown registers. This mechanism of injecting undefined
exceptions also prints a warning message for the host kernel; for example,
when a guest tries to access PMSIDR_EL1:

[    2.691830] kvm [142]: Unsupported guest sys_reg access at: 80009e78 [800003c5]
[    2.691830]  { Op0( 3), Op1( 0), CRn( 9), CRm( 9), Op2( 7), func_read },

This is unnecessary, because KVM has explicitly configured trapping of
those registers and is well aware of their existence. Prevent the warning
by adding the SPE registers to the list of registers that KVM emulates.
The access function will inject the undefined exception.

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
---
 arch/arm64/include/asm/sysreg.h |  2 ++
 arch/arm64/kvm/sys_regs.c       | 13 +++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index d4a5fca984c3..43bca834c477 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -283,6 +283,8 @@
 #define SYS_PMSIRR_EL1_INTERVAL_MASK	0xffffffUL
 
 /* Filtering controls */
+#define SYS_PMSNEVFR_EL1		sys_reg(3, 0, 9, 9, 1)
+
 #define SYS_PMSFCR_EL1			sys_reg(3, 0, 9, 9, 4)
 #define SYS_PMSFCR_EL1_FE_SHIFT		0
 #define SYS_PMSFCR_EL1_FT_SHIFT		1
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 4f2f1e3145de..402cd11aa4fc 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1501,6 +1501,19 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
 	{ SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },
 
+	{ SYS_DESC(SYS_PMSCR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMSNEVFR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMSICR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMSIRR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMSFCR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMSEVFR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMSLATFR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMSIDR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMBLIMITR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMBPTR_EL1), undef_access },
+	{ SYS_DESC(SYS_PMBSR_EL1), undef_access },
+	/* PMBIDR_EL1 is not trapped */
+
 	{ PMU_SYS_REG(SYS_PMINTENSET_EL1),
 	  .access = access_pminten, .reg = PMINTENSET_EL1 },
 	{ PMU_SYS_REG(SYS_PMINTENCLR_EL1),
-- 
2.31.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2021-04-09 15:21 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-09 15:21 [PATCH 0/2] KVM: arm64: Hide SPE from guests Alexandru Elisei
2021-04-09 15:21 ` Alexandru Elisei
2021-04-09 15:21 ` Alexandru Elisei [this message]
2021-04-09 15:21   ` [PATCH 1/2] KVM: arm64: Don't print warning when trapping SPE registers Alexandru Elisei
2021-04-09 15:21 ` [PATCH 2/2] KVM: arm64: Don't advertise FEAT_SPE to guests Alexandru Elisei
2021-04-09 15:21   ` Alexandru Elisei
2021-04-11  8:47 ` [PATCH 0/2] KVM: arm64: Hide SPE from guests Marc Zyngier
2021-04-11  8:47   ` Marc Zyngier

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