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Tue, 01 Sep 2026 01:09:58 -0700 (PDT) Date: Tue, 1 Sep 2026 09:09:31 +0100 In-Reply-To: <20260901080941.997769-1-vdonnefort@google.com> Mime-Version: 1.0 References: <20260901080941.997769-1-vdonnefort@google.com> X-Mailer: git-send-email 2.55.0.897.gb25b4bd76c-goog Message-ID: <20260901080941.997769-9-vdonnefort@google.com> Subject: [PATCH v5 08/18] KVM: arm64: Add reclaim interface for the pKVM heap alloc From: Vincent Donnefort To: maz@kernel.org, oupton@kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org Cc: joey.gouly@arm.com, seiden@linux.ibm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, kernel-team@android.com, fuad.tabba@linux.dev, qperret@google.com, Vincent Donnefort Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260901_011001_270008_25A970BE X-CRM114-Status: GOOD ( 14.39 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Introduce a host interface to reclaim donated memory from the pKVM heap allocator back to the host. It specifically provides two helpers that will make it easier to create a shrinker for pKVM: pkvm_hyp_reclaimable() pkvm_hyp_relaim() Reviewed-by: Fuad Tabba Tested-by: Fuad Tabba Signed-off-by: Vincent Donnefort diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h index de59e89318fa..fc3c52b03154 100644 --- a/arch/arm64/include/asm/kvm_asm.h +++ b/arch/arm64/include/asm/kvm_asm.h @@ -90,6 +90,8 @@ enum __kvm_host_smccc_func { __KVM_HOST_SMCCC_FUNC___vgic_v5_save_apr, __KVM_HOST_SMCCC_FUNC___vgic_v5_restore_vmcr_apr, __KVM_HOST_SMCCC_FUNC___pkvm_hyp_topup, + __KVM_HOST_SMCCC_FUNC___pkvm_hyp_reclaim, + __KVM_HOST_SMCCC_FUNC___pkvm_hyp_reclaimable, MARKER(__KVM_HOST_SMCCC_FUNC_PKVM_ONLY), diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c index 0e590261f1cc..62567560e1a5 100644 --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c @@ -851,6 +851,42 @@ static void handle___pkvm_hyp_topup(struct kvm_cpu_context *host_ctxt) cpu_reg(host_ctxt, 3) = host_mc.nr_pages; } +static void handle___pkvm_hyp_reclaim(struct kvm_cpu_context *host_ctxt) +{ + DECLARE_REG(enum pkvm_topup_id, id, host_ctxt, 1); + DECLARE_REG(unsigned long, target, host_ctxt, 2); + struct kvm_hyp_memcache host_mc = {}; + int ret = 0; + + switch (id) { + case PKVM_TOPUP_HYP_ALLOC: + hyp_alloc_reclaim(&host_mc, target); + break; + default: + ret = -EINVAL; + } + + cpu_reg(host_ctxt, 1) = ret; + cpu_reg(host_ctxt, 2) = host_mc.head; + cpu_reg(host_ctxt, 3) = host_mc.nr_pages; +} + +static void handle___pkvm_hyp_reclaimable(struct kvm_cpu_context *host_ctxt) +{ + DECLARE_REG(enum pkvm_topup_id, id, host_ctxt, 1); + unsigned long reclaimable = 0; + + switch (id) { + case PKVM_TOPUP_HYP_ALLOC: + reclaimable = hyp_alloc_reclaimable(); + break; + default: + reclaimable = 0; + } + + cpu_reg(host_ctxt, 1) = reclaimable; +} + static void handle___tracing_load(struct kvm_cpu_context *host_ctxt) { DECLARE_REG(unsigned long, desc_hva, host_ctxt, 1); @@ -960,6 +996,8 @@ static const hcall_t host_hcall[] = { HANDLE_FUNC(__vgic_v5_save_apr), HANDLE_FUNC(__vgic_v5_restore_vmcr_apr), HANDLE_FUNC(__pkvm_hyp_topup), + HANDLE_FUNC(__pkvm_hyp_reclaim), + HANDLE_FUNC(__pkvm_hyp_reclaimable), HANDLE_FUNC(__pkvm_host_share_hyp), HANDLE_FUNC(__pkvm_host_unshare_hyp), diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c index 9cd23978481c..fec819a9dc78 100644 --- a/arch/arm64/kvm/pkvm.c +++ b/arch/arm64/kvm/pkvm.c @@ -115,6 +115,50 @@ static int pkvm_hyp_topup(enum pkvm_topup_id id, unsigned long nr_pages) return ret; } +static unsigned long __pkvm_hyp_reclaim(enum pkvm_topup_id id, unsigned long target) +{ + struct kvm_hyp_memcache mc; + struct arm_smccc_res res; + unsigned long reclaimed; + + arm_smccc_1_1_hvc(KVM_HOST_SMCCC_FUNC(__pkvm_hyp_reclaim), id, target, &res); + if (WARN_ON_ONCE(res.a0 != SMCCC_RET_SUCCESS) || WARN_ON_ONCE(res.a1)) + return 0; + + init_hyp_memcache(&mc); + mc.head = res.a2; + mc.nr_pages = reclaimed = res.a3; + free_hyp_memcache(&mc); + + return reclaimed; +} + +static __maybe_unused unsigned long pkvm_hyp_reclaim(enum pkvm_topup_id id, unsigned long target) +{ + unsigned long reclaimed = 0; + + while (reclaimed < target) { + /* Arbitrary limit to avoid blocking in EL2 for too long */ + unsigned long r = __pkvm_hyp_reclaim(id, min(target - reclaimed, 16)); + + if (!r) + break; + + reclaimed += r; + if (reclaimed >= target) + break; + + cond_resched(); + } + + return reclaimed; +} + +static __maybe_unused unsigned long pkvm_hyp_reclaimable(enum pkvm_topup_id id) +{ + return kvm_call_hyp_nvhe(__pkvm_hyp_reclaimable, id); +} + static void __pkvm_destroy_hyp_vm(struct kvm *kvm) { if (pkvm_hyp_vm_is_created(kvm)) { -- 2.55.0.897.gb25b4bd76c-goog