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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Date: Mon, 22 Jun 2020 11:25:41 +0100 From: Marc Zyngier To: Mark Rutland Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, James Morse , Julien Thierry , Suzuki K Poulose , Andrew Scull , Dave Martin , kernel-team@android.com Subject: Re: [PATCH v2 5/5] KVM: arm64: Simplify PtrAuth alternative patching In-Reply-To: <20200622091508.GB88608@C02TD0UTHF1T.local> References: <20200622080643.171651-1-maz@kernel.org> <20200622080643.171651-6-maz@kernel.org> <20200622091508.GB88608@C02TD0UTHF1T.local> User-Agent: Roundcube Webmail/1.4.5 Message-ID: <422da5e4a8cfb9f9d7870d0a50985e55@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: mark.rutland@arm.com, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, ascull@google.com, Dave.Martin@arm.com, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi Mark, On 2020-06-22 10:15, Mark Rutland wrote: > On Mon, Jun 22, 2020 at 09:06:43AM +0100, Marc Zyngier wrote: >> We currently decide to execute the PtrAuth save/restore code based >> on a set of branches that evaluate as (ARM64_HAS_ADDRESS_AUTH_ARCH || >> ARM64_HAS_ADDRESS_AUTH_IMP_DEF). This can be easily replaced by >> a much simpler test as the ARM64_HAS_ADDRESS_AUTH capability is >> exactly this expression. >> >> Suggested-by: Mark Rutland >> Signed-off-by: Marc Zyngier > > Looks good to me. One minor suggestion below, but either way: > > Acked-by: Mark Rutland > >> --- >> arch/arm64/include/asm/kvm_ptrauth.h | 26 +++++++++----------------- >> 1 file changed, 9 insertions(+), 17 deletions(-) >> >> diff --git a/arch/arm64/include/asm/kvm_ptrauth.h >> b/arch/arm64/include/asm/kvm_ptrauth.h >> index f1830173fa9e..7a72508a841b 100644 >> --- a/arch/arm64/include/asm/kvm_ptrauth.h >> +++ b/arch/arm64/include/asm/kvm_ptrauth.h >> @@ -61,44 +61,36 @@ >> >> /* >> * Both ptrauth_switch_to_guest and ptrauth_switch_to_host macros >> will >> - * check for the presence of one of the cpufeature flag >> - * ARM64_HAS_ADDRESS_AUTH_ARCH or ARM64_HAS_ADDRESS_AUTH_IMP_DEF and >> + * check for the presence ARM64_HAS_ADDRESS_AUTH, which is defined as >> + * (ARM64_HAS_ADDRESS_AUTH_ARCH || ARM64_HAS_ADDRESS_AUTH_IMP_DEF) >> and >> * then proceed ahead with the save/restore of Pointer Authentication >> - * key registers. >> + * key registers if enabled for the guest. >> */ >> .macro ptrauth_switch_to_guest g_ctxt, reg1, reg2, reg3 >> -alternative_if ARM64_HAS_ADDRESS_AUTH_ARCH >> +alternative_if_not ARM64_HAS_ADDRESS_AUTH >> b 1000f >> alternative_else_nop_endif >> -alternative_if_not ARM64_HAS_ADDRESS_AUTH_IMP_DEF >> - b 1001f >> -alternative_else_nop_endif >> -1000: >> mrs \reg1, hcr_el2 >> and \reg1, \reg1, #(HCR_API | HCR_APK) >> - cbz \reg1, 1001f >> + cbz \reg1, 1000f >> add \reg1, \g_ctxt, #CPU_APIAKEYLO_EL1 >> ptrauth_restore_state \reg1, \reg2, \reg3 >> -1001: >> +1000: >> .endm > > Since these are in macros, we could use \@ to generate a macro-specific > lavel rather than a magic number, which would be less likely to > conflict > with the surrounding environment and would be more descriptive. We do > that in a few places already, and here it could look something like: > > | alternative_if_not ARM64_HAS_ADDRESS_AUTH > | b .L__skip_pauth_switch\@ > | alternative_else_nop_endif > | > | ... > | > | .L__skip_pauth_switch\@: > > Per the gas documentation > > | \@ > | > | as maintains a counter of how many macros it has executed in this > | pseudo-variable; you can copy that number to your output with > ‘\@’, > | but only within a macro definition. > > No worries if you don't want to change that now; the Acked-by stands > either way. I have folded in the following patch: diff --git a/arch/arm64/include/asm/kvm_ptrauth.h b/arch/arm64/include/asm/kvm_ptrauth.h index 7a72508a841b..0ddf98c3ba9f 100644 --- a/arch/arm64/include/asm/kvm_ptrauth.h +++ b/arch/arm64/include/asm/kvm_ptrauth.h @@ -68,29 +68,29 @@ */ .macro ptrauth_switch_to_guest g_ctxt, reg1, reg2, reg3 alternative_if_not ARM64_HAS_ADDRESS_AUTH - b 1000f + b .L__skip_switch\@ alternative_else_nop_endif mrs \reg1, hcr_el2 and \reg1, \reg1, #(HCR_API | HCR_APK) - cbz \reg1, 1000f + cbz \reg1, .L__skip_switch\@ add \reg1, \g_ctxt, #CPU_APIAKEYLO_EL1 ptrauth_restore_state \reg1, \reg2, \reg3 -1000: +.L__skip_switch\@: .endm .macro ptrauth_switch_to_host g_ctxt, h_ctxt, reg1, reg2, reg3 alternative_if_not ARM64_HAS_ADDRESS_AUTH - b 2000f + b .L__skip_switch\@ alternative_else_nop_endif mrs \reg1, hcr_el2 and \reg1, \reg1, #(HCR_API | HCR_APK) - cbz \reg1, 2000f + cbz \reg1, .L__skip_switch\@ add \reg1, \g_ctxt, #CPU_APIAKEYLO_EL1 ptrauth_save_state \reg1, \reg2, \reg3 add \reg1, \h_ctxt, #CPU_APIAKEYLO_EL1 ptrauth_restore_state \reg1, \reg2, \reg3 isb -2000: +.L__skip_switch\@: .endm #else /* !CONFIG_ARM64_PTR_AUTH */ Thanks, M. -- Jazz is not dead. It just smells funny...