From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x227JSn+uL3PHshTAPm0LSGWmmCDM/XxLRV7cC3Fi5nJrMaMMuW3mY9CDjol0zcxI2Tm11Gs/ ARC-Seal: i=1; a=rsa-sha256; t=1517920776; cv=none; d=google.com; s=arc-20160816; b=a8cvbx3da7Df8DYXN/vF13Xa/tYWSevdFQjU2yDiD9eRyST+rVqAjTe/l56d07qcv8 7nFGJGF0GaWpz/OYD7KM0tcGdVRXhJOCOpMZ+StOq88KDPQyf012yGev2IbFWjpL5/WG 54ob/PVz3kP/92PY8F9UINWnnJ7GCS2RAoP+4q0y1WqWuj99n3Xok56TUP4E3VVNEX2N nvwoPpHJqDWf3EGUxWsiI6QHMiGc8GjdIvyN307BsyWp38bdgLbIsZpYUB2msupEMowl zURkL+jdX7Cqh6dNSl0mzdeFta6iCb/fNwbeWdR1H9hoX2jTQ9TBZl1w7muQBnhV40Zi jO4w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:dkim-signature:delivered-to :list-id:list-subscribe:list-unsubscribe:list-help:list-post :precedence:mailing-list:arc-authentication-results; bh=GnAcEgvQpCXFmD9STRBGepRB+RtNNhxWDS6dfeuO55k=; b=Y2yWWW1ht8OpYKL+7I397odLmwPOozMuwTQ23E1oK7RiRKjSLw9ogiGbWbifMfMHwk nK9rWKU7NFMY29KheNYPGXcLEawu7yrZQcG+5/mQnfMP+EAFSqG0nx2XWTYWw1maZK3S ItrojTAvTO4hhsN5UgumolTUit1uwuxr4P+doizsjz1Ym0MqgeBZwX4eLVN0FaV0f+TX JRWjBzld//1oPEFRMCMIVPVczCmj+vAfyk1ku86+OHNWqODx1xNLTHBuBhB8khUi+z6a yiQDSJsFkd+HVEW6+Rq+b3kEmwJSCIyAJDfnvDP1eX6vslA4GwQulSWDI7oHd1L/UNcs UTJw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b=fPowP1ks; spf=pass (google.com: domain of kernel-hardening-return-11631-gregkh=linuxfoundation.org@lists.openwall.com designates 195.42.179.200 as permitted sender) smtp.mailfrom=kernel-hardening-return-11631-gregkh=linuxfoundation.org@lists.openwall.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Authentication-Results: mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b=fPowP1ks; spf=pass (google.com: domain of kernel-hardening-return-11631-gregkh=linuxfoundation.org@lists.openwall.com designates 195.42.179.200 as permitted sender) smtp.mailfrom=kernel-hardening-return-11631-gregkh=linuxfoundation.org@lists.openwall.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm List-Post: List-Help: List-Unsubscribe: List-Subscribe: Date: Tue, 6 Feb 2018 13:39:15 +0100 From: Christoffer Dall To: Mark Rutland Cc: linux-arm-kernel@lists.infradead.org, arnd@arndb.de, catalin.marinas@arm.com, cdall@linaro.org, kvmarm@lists.cs.columbia.edu, linux-arch@vger.kernel.org, marc.zyngier@arm.com, suzuki.poulose@arm.com, will.deacon@arm.com, yao.qi@arm.com, kernel-hardening@lists.openwall.com, linux-kernel@vger.kernel.org, awallis@codeaurora.org Subject: Re: [PATCHv2 09/12] arm64/kvm: preserve host HCR_EL2 value Message-ID: <20180206123915.GA21802@cbox> References: <20171127163806.31435-1-mark.rutland@arm.com> <20171127163806.31435-10-mark.rutland@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171127163806.31435-10-mark.rutland@arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1585238090523877601?= X-GMAIL-MSGID: =?utf-8?q?1591655296650373013?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Mon, Nov 27, 2017 at 04:38:03PM +0000, Mark Rutland wrote: > When restoring HCR_EL2 for the host, KVM uses HCR_HOST_VHE_FLAGS, which > is a constant value. This works today, as the host HCR_EL2 value is > always the same, but this will get in the way of supporting extensions > that require HCR_EL2 bits to be set conditionally for the host. > > To allow such features to work without KVM having to explicitly handle > every possible host feature combination, this patch has KVM save/restore > the host HCR when switching to/from a guest HCR. > > For __{activate,deactivate}_traps(), the HCR save/restore is made common > across the !VHE and VHE paths. As the host and guest HCR values must > have E2H set when VHE is in use, register redirection should always be > in effect at EL2, and this change should not adversely affect the VHE > code. > > For the hyp TLB maintenance code, __tlb_switch_to_host_vhe() is updated > to toggle the TGE bit with a RMW sequence, as we already do in > __tlb_switch_to_guest_vhe(). > > The now unused HCR_HOST_VHE_FLAGS definition is removed. > > Signed-off-by: Mark Rutland > Reviewed-by: Christoffer Dall > Cc: Marc Zyngier > Cc: kvmarm@lists.cs.columbia.edu > --- > arch/arm64/include/asm/kvm_arm.h | 1 - > arch/arm64/include/asm/kvm_host.h | 5 ++++- > arch/arm64/kvm/hyp/switch.c | 5 +++-- > arch/arm64/kvm/hyp/tlb.c | 6 +++++- > 4 files changed, 12 insertions(+), 5 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h > index 62854d5d1d3b..aa02b05430e8 100644 > --- a/arch/arm64/include/asm/kvm_arm.h > +++ b/arch/arm64/include/asm/kvm_arm.h > @@ -84,7 +84,6 @@ > HCR_AMO | HCR_SWIO | HCR_TIDCP | HCR_RW) > #define HCR_VIRT_EXCP_MASK (HCR_VSE | HCR_VI | HCR_VF) > #define HCR_INT_OVERRIDE (HCR_FMO | HCR_IMO) > -#define HCR_HOST_VHE_FLAGS (HCR_RW | HCR_TGE | HCR_E2H) > > /* TCR_EL2 Registers bits */ > #define TCR_EL2_RES1 ((1 << 31) | (1 << 23)) > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index 674912d7a571..39184aa3e2f2 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -199,10 +199,13 @@ typedef struct kvm_cpu_context kvm_cpu_context_t; > struct kvm_vcpu_arch { > struct kvm_cpu_context ctxt; > > - /* HYP configuration */ > + /* Guest HYP configuration */ > u64 hcr_el2; > u32 mdcr_el2; > > + /* Host HYP configuration */ > + u64 host_hcr_el2; > + > /* Exception Information */ > struct kvm_vcpu_fault_info fault; > > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c > index 525c01f48867..2205f0be3ced 100644 > --- a/arch/arm64/kvm/hyp/switch.c > +++ b/arch/arm64/kvm/hyp/switch.c > @@ -71,6 +71,8 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu) > { > u64 val; > > + vcpu->arch.host_hcr_el2 = read_sysreg(hcr_el2); > + Looking back at this, it seems excessive to switch this at every round-trip. I think it should be possible to have this as a single global (or per-CPU) variable that gets restored directly when returning from the VM. Thanks, -Christoffer > /* > * We are about to set CPTR_EL2.TFP to trap all floating point > * register accesses to EL2, however, the ARM ARM clearly states that > @@ -116,7 +118,6 @@ static void __hyp_text __deactivate_traps_vhe(void) > MDCR_EL2_TPMS; > > write_sysreg(mdcr_el2, mdcr_el2); > - write_sysreg(HCR_HOST_VHE_FLAGS, hcr_el2); > write_sysreg(CPACR_EL1_DEFAULT, cpacr_el1); > write_sysreg(vectors, vbar_el1); > } > @@ -129,7 +130,6 @@ static void __hyp_text __deactivate_traps_nvhe(void) > mdcr_el2 |= MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT; > > write_sysreg(mdcr_el2, mdcr_el2); > - write_sysreg(HCR_RW, hcr_el2); > write_sysreg(CPTR_EL2_DEFAULT, cptr_el2); > } > > @@ -151,6 +151,7 @@ static void __hyp_text __deactivate_traps(struct kvm_vcpu *vcpu) > __deactivate_traps_arch()(); > write_sysreg(0, hstr_el2); > write_sysreg(0, pmuserenr_el0); > + write_sysreg(vcpu->arch.host_hcr_el2, hcr_el2); > } > > static void __hyp_text __activate_vm(struct kvm_vcpu *vcpu) > diff --git a/arch/arm64/kvm/hyp/tlb.c b/arch/arm64/kvm/hyp/tlb.c > index 73464a96c365..c2b0680efa2c 100644 > --- a/arch/arm64/kvm/hyp/tlb.c > +++ b/arch/arm64/kvm/hyp/tlb.c > @@ -49,12 +49,16 @@ static hyp_alternate_select(__tlb_switch_to_guest, > > static void __hyp_text __tlb_switch_to_host_vhe(struct kvm *kvm) > { > + u64 val; > + > /* > * We're done with the TLB operation, let's restore the host's > * view of HCR_EL2. > */ > write_sysreg(0, vttbr_el2); > - write_sysreg(HCR_HOST_VHE_FLAGS, hcr_el2); > + val = read_sysreg(hcr_el2); > + val |= HCR_TGE; > + write_sysreg(val, hcr_el2); > } > > static void __hyp_text __tlb_switch_to_host_nvhe(struct kvm *kvm) > -- > 2.11.0 >