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Fri, 10 Dec 2021 06:48:56 -0800 (PST) Date: Fri, 10 Dec 2021 14:48:53 +0000 From: Quentin Perret To: Will Deacon Cc: Marc Zyngier , James Morse , Alexandru Elisei , Suzuki K Poulose , Catalin Marinas , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v3 15/15] KVM: arm64: pkvm: Unshare guest structs during teardown Message-ID: References: <20211201170411.1561936-1-qperret@google.com> <20211201170411.1561936-16-qperret@google.com> <20211209112233.GD1912@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20211209112233.GD1912@willie-the-truck> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211210_064859_754714_E0A42102 X-CRM114-Status: GOOD ( 25.46 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thursday 09 Dec 2021 at 11:22:33 (+0000), Will Deacon wrote: > On Wed, Dec 01, 2021 at 05:04:09PM +0000, Quentin Perret wrote: > > Make use of the newly introduced unshare hypercall during guest teardown > > to unmap guest-related data structures from the hyp stage-1. > > > > Signed-off-by: Quentin Perret > > --- > > arch/arm64/include/asm/kvm_host.h | 2 ++ > > arch/arm64/include/asm/kvm_mmu.h | 1 + > > arch/arm64/kvm/arm.c | 2 ++ > > arch/arm64/kvm/fpsimd.c | 34 ++++++++++++++++++++++--- > > arch/arm64/kvm/mmu.c | 42 +++++++++++++++++++++++++++++++ > > arch/arm64/kvm/reset.c | 8 +++++- > > 6 files changed, 85 insertions(+), 4 deletions(-) > > [...] > > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > > index d72566896755..8e506ba8988e 100644 > > --- a/arch/arm64/kvm/mmu.c > > +++ b/arch/arm64/kvm/mmu.c > > @@ -344,6 +344,32 @@ static int share_pfn_hyp(u64 pfn) > > return ret; > > } > > > > +static int unshare_pfn_hyp(u64 pfn) > > +{ > > + struct rb_node **node, *parent; > > + struct hyp_shared_pfn *this; > > + int ret = 0; > > + > > + mutex_lock(&hyp_shared_pfns_lock); > > + this = find_shared_pfn(pfn, &node, &parent); > > + if (WARN_ON(!this)) { > > + ret = -EINVAL; > > -ENOENT? Sure. > > + goto unlock; > > + } > > + > > + this->count--; > > + if (this->count) > > + goto unlock; > > Again, if we did an RCU lookup then this could be converted to a refcount_t > to take the mutex only when it hits zero. But for now I think it's fine. No objection to do this in the future, but yeah I think we might as well start simple :) > > + > > + rb_erase(&this->node, &hyp_shared_pfns); > > + kfree(this); > > + ret = kvm_call_hyp_nvhe(__pkvm_host_unshare_hyp, pfn, 1); > > +unlock: > > + mutex_unlock(&hyp_shared_pfns_lock); > > + > > + return ret; > > +} > > + > > int kvm_share_hyp(void *from, void *to) > > { > > phys_addr_t start, end, cur; > > @@ -376,6 +402,22 @@ int kvm_share_hyp(void *from, void *to) > > return 0; > > } > > > > +void kvm_unshare_hyp(void *from, void *to) > > +{ > > + phys_addr_t start, end, cur; > > + u64 pfn; > > + > > + if (is_kernel_in_hyp_mode() || kvm_host_owns_hyp_mappings() || !from) > > I don't think you need the is_kernel_in_hyp_mode() check any more not that > you've moved that into kvm_host_owns_hyp_mappings(). The logic is a little odd, but I think I still do as kvm_host_owns_hyp_mappings() will return false if is_kernel_in_hyp_mode() is true. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel