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Tue, 10 Mar 2026 05:49:56 -0700 (PDT) Date: Tue, 10 Mar 2026 12:49:31 +0000 In-Reply-To: <20260310124933.830025-1-sebastianene@google.com> Mime-Version: 1.0 References: <20260310124933.830025-1-sebastianene@google.com> X-Mailer: git-send-email 2.53.0.473.g4a7958ca14-goog Message-ID: <20260310124933.830025-13-sebastianene@google.com> Subject: [PATCH 12/14] KVM: arm64: Restrict host updates to GITS_CBASER From: Sebastian Ene To: alexandru.elisei@arm.com, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, android-kvm@google.com Cc: catalin.marinas@arm.com, dbrazdil@google.com, joey.gouly@arm.com, kees@kernel.org, mark.rutland@arm.com, maz@kernel.org, oupton@kernel.org, perlarsen@google.com, qperret@google.com, rananta@google.com, sebastianene@google.com, smostafa@google.com, suzuki.poulose@arm.com, tabba@google.com, tglx@kernel.org, vdonnefort@google.com, bgrzesik@google.com, will@kernel.org, yuzenghui@huawei.com Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260310_054959_321863_30EF2DFD X-CRM114-Status: GOOD ( 12.28 ) 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 Prevent the host from updating the ITS command queue base address (GITS_CBASER) while the ITS is enabled or not in a quiescent state. This enforcement prevents unpredictable hardware behavior and ensures the host cannot update the hardware with a new queue address behind the hypervisor's back, which would bypass the command queue shadowing mechanism. Signed-off-by: Sebastian Ene --- arch/arm64/kvm/hyp/nvhe/its_emulate.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/arch/arm64/kvm/hyp/nvhe/its_emulate.c b/arch/arm64/kvm/hyp/nvhe/its_emulate.c index 539d2ee3b58e..9715f15cd432 100644 --- a/arch/arm64/kvm/hyp/nvhe/its_emulate.c +++ b/arch/arm64/kvm/hyp/nvhe/its_emulate.c @@ -291,6 +291,30 @@ static void ctlr_write(struct its_priv_state *its, u64 offset, u64 value) writeq_relaxed(value, its->base + GITS_CTLR); } +static void cbaser_write(struct its_priv_state *its, u64 offset, u64 value) +{ + u64 ctlr = readq_relaxed(its->base + GITS_CTLR); + int num_pages; + + if ((ctlr & GITS_CTLR_ENABLE) || + !(ctlr & GITS_CTLR_QUIESCENT)) + return; + + num_pages = its->shadow->cmdq_len / SZ_4K; + value &= ~GENMASK(7, 0) | ~GENMASK_ULL(51, 12); + + value |= (num_pages - 1) & GENMASK(7, 0); + value |= __hyp_pa(its->cmd_hyp_base) & GENMASK_ULL(51, 12); + + its->cmd_host_cwriter = its->cmd_host_base; + writeq_relaxed(value, its->base + GITS_CBASER); +} + +static void cbaser_read(struct its_priv_state *its, u64 offset, u64 *read) +{ + *read = readq_relaxed(its->base + GITS_CBASER); +} + #define ITS_HANDLER(off, sz, write_cb, read_cb) \ { \ .offset = (off), \ @@ -302,6 +326,7 @@ static void ctlr_write(struct its_priv_state *its, u64 offset, u64 value) static struct its_handler its_handlers[] = { ITS_HANDLER(GITS_CWRITER, sizeof(u64), cwriter_write, cwriter_read), ITS_HANDLER(GITS_CTLR, sizeof(u64), ctlr_write, ctlr_read), + ITS_HANDLER(GITS_CBASER, sizeof(u64), cbaser_write, cbaser_read), {}, }; -- 2.53.0.473.g4a7958ca14-goog