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Message-ID: <b8f2fe15e0cab5c24094915b8c000930@kernel.org>
Date: Tue, 17 Nov 2020 19:20:34 +0000
From: Marc Zyngier <maz@...nel.org>
To: Steven Price <steven.price@....com>
Cc: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
James Morse <james.morse@....com>,
Julien Thierry <julien.thierry.kdev@...il.com>,
Suzuki K Poulose <suzuki.poulose@....com>,
kvmarm@...ts.cs.columbia.edu, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, Dave Martin <Dave.Martin@....com>,
Mark Rutland <mark.rutland@....com>,
Thomas Gleixner <tglx@...utronix.de>, qemu-devel@...gnu.org,
Juan Quintela <quintela@...hat.com>,
"Dr. David Alan Gilbert" <dgilbert@...hat.com>,
Richard Henderson <richard.henderson@...aro.org>,
Peter Maydell <peter.maydell@...aro.org>,
Haibo Xu <Haibo.Xu@....com>, Andrew Jones <drjones@...hat.com>
Subject: Re: [PATCH v4 1/2] arm64: kvm: Save/restore MTE registers
Hi Steven,
These patches unfortunately don't apply to -rc4 anymore, as we repainted
quite a bit while working on fixes. I'd be grateful if you could rebase
them.
A few other things though:
On 2020-10-26 15:57, Steven Price wrote:
> Define the new system registers that MTE introduces and context switch
> them. The MTE feature is still hidden from the ID register as it isn't
> supported in a VM yet.
>
> Signed-off-by: Steven Price <steven.price@....com>
> Reviewed-by: Andrew Jones <drjones@...hat.com>
> ---
> arch/arm64/include/asm/kvm_host.h | 4 ++++
> arch/arm64/include/asm/sysreg.h | 3 ++-
> arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 14 ++++++++++++++
> arch/arm64/kvm/sys_regs.c | 14 ++++++++++----
> 4 files changed, 30 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h
> b/arch/arm64/include/asm/kvm_host.h
> index 0aecbab6a7fb..95ab7345dcc8 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -134,6 +134,8 @@ enum vcpu_sysreg {
> SCTLR_EL1, /* System Control Register */
> ACTLR_EL1, /* Auxiliary Control Register */
> CPACR_EL1, /* Coprocessor Access Control */
> + RGSR_EL1, /* Random Allocation Tag Seed Register */
> + GCR_EL1, /* Tag Control Register */
> ZCR_EL1, /* SVE Control */
> TTBR0_EL1, /* Translation Table Base Register 0 */
> TTBR1_EL1, /* Translation Table Base Register 1 */
> @@ -150,6 +152,8 @@ enum vcpu_sysreg {
> TPIDR_EL1, /* Thread ID, Privileged */
> AMAIR_EL1, /* Aux Memory Attribute Indirection Register */
> CNTKCTL_EL1, /* Timer Control Register (EL1) */
> + TFSRE0_EL1, /* Tag Fault Status Register (EL0) */
> + TFSR_EL1, /* Tag Fault Stauts Register (EL1) */
> PAR_EL1, /* Physical Address Register */
> MDSCR_EL1, /* Monitor Debug System Control Register */
> MDCCINT_EL1, /* Monitor Debug Comms Channel Interrupt Enable Reg */
> diff --git a/arch/arm64/include/asm/sysreg.h
> b/arch/arm64/include/asm/sysreg.h
> index d52c1b3ce589..7727df0bc09d 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -565,7 +565,8 @@
> #define SCTLR_ELx_M (BIT(0))
>
> #define SCTLR_ELx_FLAGS (SCTLR_ELx_M | SCTLR_ELx_A | SCTLR_ELx_C | \
> - SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB)
> + SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB | \
> + SCTLR_ELx_ITFSB)
>
> /* SCTLR_EL2 specific flags. */
> #define SCTLR_EL2_RES1 ((BIT(4)) | (BIT(5)) | (BIT(11)) | (BIT(16))
> | \
> diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> index 7a986030145f..a124ffa49ba3 100644
> --- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> +++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> @@ -18,6 +18,11 @@
> static inline void __sysreg_save_common_state(struct kvm_cpu_context
> *ctxt)
> {
> ctxt_sys_reg(ctxt, MDSCR_EL1) = read_sysreg(mdscr_el1);
> + if (system_supports_mte()) {
> + ctxt_sys_reg(ctxt, RGSR_EL1) = read_sysreg_s(SYS_RGSR_EL1);
> + ctxt_sys_reg(ctxt, GCR_EL1) = read_sysreg_s(SYS_GCR_EL1);
> + ctxt_sys_reg(ctxt, TFSRE0_EL1) = read_sysreg_s(SYS_TFSRE0_EL1);
As far as I can tell, HCR_EL2.ATA is still clear when running a guest.
So why, do we save/restore this state yet?
Also, I wonder whether we should keep these in the C code. If one day
we enable MTE in the kernel, we will have to move them to the assembly
part, much like we do for PAuth. And I fear that "one day" is pretty
soon:
https://lore.kernel.org/linux-arm-kernel/cover.1605046192.git.andreyknvl@google.com/
> + }
> }
>
> static inline void __sysreg_save_user_state(struct kvm_cpu_context
> *ctxt)
> @@ -45,6 +50,8 @@ static inline void __sysreg_save_el1_state(struct
> kvm_cpu_context *ctxt)
> ctxt_sys_reg(ctxt, CNTKCTL_EL1) = read_sysreg_el1(SYS_CNTKCTL);
> ctxt_sys_reg(ctxt, PAR_EL1) = read_sysreg(par_el1);
> ctxt_sys_reg(ctxt, TPIDR_EL1) = read_sysreg(tpidr_el1);
> + if (system_supports_mte())
> + ctxt_sys_reg(ctxt, TFSR_EL1) = read_sysreg_el1(SYS_TFSR);
>
> ctxt_sys_reg(ctxt, SP_EL1) = read_sysreg(sp_el1);
> ctxt_sys_reg(ctxt, ELR_EL1) = read_sysreg_el1(SYS_ELR);
> @@ -63,6 +70,11 @@ static inline void
> __sysreg_save_el2_return_state(struct kvm_cpu_context *ctxt)
> static inline void __sysreg_restore_common_state(struct
> kvm_cpu_context *ctxt)
> {
> write_sysreg(ctxt_sys_reg(ctxt, MDSCR_EL1), mdscr_el1);
> + if (system_supports_mte()) {
> + write_sysreg_s(ctxt_sys_reg(ctxt, RGSR_EL1), SYS_RGSR_EL1);
> + write_sysreg_s(ctxt_sys_reg(ctxt, GCR_EL1), SYS_GCR_EL1);
> + write_sysreg_s(ctxt_sys_reg(ctxt, TFSRE0_EL1), SYS_TFSRE0_EL1);
> + }
> }
>
> static inline void __sysreg_restore_user_state(struct kvm_cpu_context
> *ctxt)
> @@ -106,6 +118,8 @@ static inline void
> __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
> write_sysreg_el1(ctxt_sys_reg(ctxt, CNTKCTL_EL1), SYS_CNTKCTL);
> write_sysreg(ctxt_sys_reg(ctxt, PAR_EL1), par_el1);
> write_sysreg(ctxt_sys_reg(ctxt, TPIDR_EL1), tpidr_el1);
> + if (system_supports_mte())
> + write_sysreg_el1(ctxt_sys_reg(ctxt, TFSR_EL1), SYS_TFSR);
>
> if (!has_vhe() &&
> cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT) &&
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index d9117bc56237..430e36e1a13d 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1391,6 +1391,12 @@ static bool access_mte_regs(struct kvm_vcpu
> *vcpu, struct sys_reg_params *p,
> return false;
> }
>
> +static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
> + const struct sys_reg_desc *rd)
> +{
> + return REG_HIDDEN_USER | REG_HIDDEN_GUEST;
The handling of visibility has changed somehow since 01fe5ace92dd.
> +}
> +
> /* sys_reg_desc initialiser for known cpufeature ID registers */
> #define ID_SANITISED(name) { \
> SYS_DESC(SYS_##name), \
> @@ -1557,8 +1563,8 @@ static const struct sys_reg_desc sys_reg_descs[]
> = {
> { SYS_DESC(SYS_ACTLR_EL1), access_actlr, reset_actlr, ACTLR_EL1 },
> { SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 },
>
> - { SYS_DESC(SYS_RGSR_EL1), access_mte_regs },
> - { SYS_DESC(SYS_GCR_EL1), access_mte_regs },
> + { SYS_DESC(SYS_RGSR_EL1), access_mte_regs, reset_unknown, RGSR_EL1,
> .visibility = mte_visibility },
> + { SYS_DESC(SYS_GCR_EL1), access_mte_regs, reset_unknown, GCR_EL1,
> .visibility = mte_visibility },
>
> { SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility =
> sve_visibility },
> { SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
> @@ -1584,8 +1590,8 @@ static const struct sys_reg_desc sys_reg_descs[]
> = {
> { SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi },
> { SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi },
>
> - { SYS_DESC(SYS_TFSR_EL1), access_mte_regs },
> - { SYS_DESC(SYS_TFSRE0_EL1), access_mte_regs },
> + { SYS_DESC(SYS_TFSR_EL1), access_mte_regs, reset_unknown, TFSR_EL1,
> .visibility = mte_visibility },
> + { SYS_DESC(SYS_TFSRE0_EL1), access_mte_regs, reset_unknown,
> TFSRE0_EL1, .visibility = mte_visibility },
>
> { SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 },
> { SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 },
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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