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Message-ID: <20240911143421.85612-5-faresx@amazon.de> Date: Wed, 11 Sep 2024 14:34:03 +0000 From: Fares Mehanna <faresx@...zon.de> To: CC: <nh-open-source@...zon.com>, Fares Mehanna <faresx@...zon.de>, "Marc Zyngier" <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, James Morse <james.morse@....com>, Suzuki K Poulose <suzuki.poulose@....com>, Zenghui Yu <yuzenghui@...wei.com>, Catalin Marinas <catalin.marinas@....com>, "Will Deacon" <will@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, "Kemeng Shi" <shikemeng@...weicloud.com>, Pierre-Clément Tosi <ptosi@...gle.com>, Ard Biesheuvel <ardb@...nel.org>, Mark Rutland <mark.rutland@....com>, Javier Martinez Canillas <javierm@...hat.com>, "Arnd Bergmann" <arnd@...db.de>, Fuad Tabba <tabba@...gle.com>, Mark Brown <broonie@...nel.org>, Joey Gouly <joey.gouly@....com>, Kristina Martsenko <kristina.martsenko@....com>, Randy Dunlap <rdunlap@...radead.org>, "Bjorn Helgaas" <bhelgaas@...gle.com>, Jean-Philippe Brucker <jean-philippe@...aro.org>, "Mike Rapoport (IBM)" <rppt@...nel.org>, "David Hildenbrand" <david@...hat.com>, Roman Kagan <rkagan@...zon.de>, "moderated list:KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)" <linux-arm-kernel@...ts.infradead.org>, "open list:KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)" <kvmarm@...ts.linux.dev>, open list <linux-kernel@...r.kernel.org>, "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org> Subject: [RFC PATCH 4/7] KVM: Refactor Assembly-code to access vCPU gp-registers through a macro Right now assembly code accesses vCPU gp-regs directly from the context struct "struct kvm_cpu_context" using "CPU_XREG_OFFSET()". Since we want to move gp-regs to dynamic memory, we can no longer assume that gp-regs will be embedded in the context struct, thus split the access to two steps. The first is to get the gp-regs from the context using the assembly macro "get_ctxt_gp_regs". And the second is to access the gp-registers directly from within the "struct user_pt_regs" by removing the offset "CPU_USER_PT_REGS" from the access macro "CPU_XREG_OFFSET()". I also changed variable naming and comments where appropriate. Signed-off-by: Fares Mehanna <faresx@...zon.de> --- arch/arm64/include/asm/kvm_asm.h | 48 +++++++++++++++++--------------- arch/arm64/kvm/hyp/entry.S | 15 ++++++++++ arch/arm64/kvm/hyp/nvhe/host.S | 20 ++++++++++--- 3 files changed, 57 insertions(+), 26 deletions(-) diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h index 2181a11b9d92..fa4fb642a5f5 100644 --- a/arch/arm64/include/asm/kvm_asm.h +++ b/arch/arm64/include/asm/kvm_asm.h @@ -313,6 +313,10 @@ void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr, u64 elr_virt, str \vcpu, [\ctxt, #HOST_CONTEXT_VCPU] .endm +.macro get_ctxt_gp_regs ctxt, regs + add \regs, \ctxt, #CPU_USER_PT_REGS +.endm + /* * KVM extable for unexpected exceptions. * Create a struct kvm_exception_table_entry output to a section that can be @@ -329,7 +333,7 @@ void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr, u64 elr_virt, .popsection .endm -#define CPU_XREG_OFFSET(x) (CPU_USER_PT_REGS + 8*x) +#define CPU_XREG_OFFSET(x) (8 * (x)) #define CPU_LR_OFFSET CPU_XREG_OFFSET(30) #define CPU_SP_EL0_OFFSET (CPU_LR_OFFSET + 8) @@ -337,34 +341,34 @@ void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr, u64 elr_virt, * We treat x18 as callee-saved as the host may use it as a platform * register (e.g. for shadow call stack). */ -.macro save_callee_saved_regs ctxt - str x18, [\ctxt, #CPU_XREG_OFFSET(18)] - stp x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)] - stp x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)] - stp x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)] - stp x25, x26, [\ctxt, #CPU_XREG_OFFSET(25)] - stp x27, x28, [\ctxt, #CPU_XREG_OFFSET(27)] - stp x29, lr, [\ctxt, #CPU_XREG_OFFSET(29)] +.macro save_callee_saved_regs regs + str x18, [\regs, #CPU_XREG_OFFSET(18)] + stp x19, x20, [\regs, #CPU_XREG_OFFSET(19)] + stp x21, x22, [\regs, #CPU_XREG_OFFSET(21)] + stp x23, x24, [\regs, #CPU_XREG_OFFSET(23)] + stp x25, x26, [\regs, #CPU_XREG_OFFSET(25)] + stp x27, x28, [\regs, #CPU_XREG_OFFSET(27)] + stp x29, lr, [\regs, #CPU_XREG_OFFSET(29)] .endm -.macro restore_callee_saved_regs ctxt - // We require \ctxt is not x18-x28 - ldr x18, [\ctxt, #CPU_XREG_OFFSET(18)] - ldp x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)] - ldp x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)] - ldp x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)] - ldp x25, x26, [\ctxt, #CPU_XREG_OFFSET(25)] - ldp x27, x28, [\ctxt, #CPU_XREG_OFFSET(27)] - ldp x29, lr, [\ctxt, #CPU_XREG_OFFSET(29)] +.macro restore_callee_saved_regs regs + // We require \regs is not x18-x28 + ldr x18, [\regs, #CPU_XREG_OFFSET(18)] + ldp x19, x20, [\regs, #CPU_XREG_OFFSET(19)] + ldp x21, x22, [\regs, #CPU_XREG_OFFSET(21)] + ldp x23, x24, [\regs, #CPU_XREG_OFFSET(23)] + ldp x25, x26, [\regs, #CPU_XREG_OFFSET(25)] + ldp x27, x28, [\regs, #CPU_XREG_OFFSET(27)] + ldp x29, lr, [\regs, #CPU_XREG_OFFSET(29)] .endm -.macro save_sp_el0 ctxt, tmp +.macro save_sp_el0 regs, tmp mrs \tmp, sp_el0 - str \tmp, [\ctxt, #CPU_SP_EL0_OFFSET] + str \tmp, [\regs, #CPU_SP_EL0_OFFSET] .endm -.macro restore_sp_el0 ctxt, tmp - ldr \tmp, [\ctxt, #CPU_SP_EL0_OFFSET] +.macro restore_sp_el0 regs, tmp + ldr \tmp, [\regs, #CPU_SP_EL0_OFFSET] msr sp_el0, \tmp .endm diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S index 4433a234aa9b..628a123bcdc1 100644 --- a/arch/arm64/kvm/hyp/entry.S +++ b/arch/arm64/kvm/hyp/entry.S @@ -28,6 +28,9 @@ SYM_FUNC_START(__guest_enter) adr_this_cpu x1, kvm_hyp_ctxt, x2 + // Get gp-regs pointer from the context + get_ctxt_gp_regs x1, x1 + // Store the hyp regs save_callee_saved_regs x1 @@ -62,6 +65,9 @@ alternative_else_nop_endif // when this feature is enabled for kernel code. ptrauth_switch_to_guest x29, x0, x1, x2 + // Get gp-regs pointer from the context + get_ctxt_gp_regs x29, x29 + // Restore the guest's sp_el0 restore_sp_el0 x29, x0 @@ -108,6 +114,7 @@ SYM_INNER_LABEL(__guest_exit_panic, SYM_L_GLOBAL) // current state is saved to the guest context but it will only be // accurate if the guest had been completely restored. adr_this_cpu x0, kvm_hyp_ctxt, x1 + get_ctxt_gp_regs x0, x0 adr_l x1, hyp_panic str x1, [x0, #CPU_XREG_OFFSET(30)] @@ -120,6 +127,7 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL) // vcpu x0-x1 on the stack add x1, x1, #VCPU_CONTEXT + get_ctxt_gp_regs x1, x1 ALTERNATIVE(nop, SET_PSTATE_PAN(1), ARM64_HAS_PAN, CONFIG_ARM64_PAN) @@ -145,6 +153,10 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL) // Store the guest's sp_el0 save_sp_el0 x1, x2 + // Recover vCPU context to x1 + get_vcpu_ptr x1, x2 + add x1, x1, #VCPU_CONTEXT + adr_this_cpu x2, kvm_hyp_ctxt, x3 // Macro ptrauth_switch_to_hyp format: @@ -157,6 +169,9 @@ SYM_INNER_LABEL(__guest_exit, SYM_L_GLOBAL) // mte_switch_to_hyp(g_ctxt, h_ctxt, reg1) mte_switch_to_hyp x1, x2, x3 + // Get gp-regs pointer from the context + get_ctxt_gp_regs x2, x2 + // Restore hyp's sp_el0 restore_sp_el0 x2, x3 diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S index 3d610fc51f4d..31afa7396294 100644 --- a/arch/arm64/kvm/hyp/nvhe/host.S +++ b/arch/arm64/kvm/hyp/nvhe/host.S @@ -17,6 +17,12 @@ SYM_FUNC_START(__host_exit) get_host_ctxt x0, x1 + /* Keep host context in x1 */ + mov x1, x0 + + /* Get gp-regs pointer from the context */ + get_ctxt_gp_regs x0, x0 + /* Store the host regs x2 and x3 */ stp x2, x3, [x0, #CPU_XREG_OFFSET(2)] @@ -36,7 +42,10 @@ SYM_FUNC_START(__host_exit) /* Store the host regs x18-x29, lr */ save_callee_saved_regs x0 - /* Save the host context pointer in x29 across the function call */ + /* Save the host context pointer in x28 across the function call */ + mov x28, x1 + + /* Save the host gp-regs pointer in x29 across the function call */ mov x29, x0 #ifdef CONFIG_ARM64_PTR_AUTH_KERNEL @@ -46,7 +55,7 @@ alternative_else_nop_endif alternative_if ARM64_KVM_PROTECTED_MODE /* Save kernel ptrauth keys. */ - add x18, x29, #CPU_APIAKEYLO_EL1 + add x18, x28, #CPU_APIAKEYLO_EL1 ptrauth_save_state x18, x19, x20 /* Use hyp keys. */ @@ -58,6 +67,7 @@ alternative_else_nop_endif __skip_pauth_save: #endif /* CONFIG_ARM64_PTR_AUTH_KERNEL */ + mov x0, x28 bl handle_trap __host_enter_restore_full: @@ -68,7 +78,7 @@ b __skip_pauth_restore alternative_else_nop_endif alternative_if ARM64_KVM_PROTECTED_MODE - add x18, x29, #CPU_APIAKEYLO_EL1 + add x18, x28, #CPU_APIAKEYLO_EL1 ptrauth_restore_state x18, x19, x20 alternative_else_nop_endif __skip_pauth_restore: @@ -101,7 +111,8 @@ SYM_FUNC_END(__host_exit) * void __noreturn __host_enter(struct kvm_cpu_context *host_ctxt); */ SYM_FUNC_START(__host_enter) - mov x29, x0 + mov x28, x0 + get_ctxt_gp_regs x0, x29 b __host_enter_restore_full SYM_FUNC_END(__host_enter) @@ -141,6 +152,7 @@ SYM_FUNC_START(__hyp_do_panic) /* Enter the host, conditionally restoring the host context. */ cbz x29, __host_enter_without_restoring + get_ctxt_gp_regs x29, x29 b __host_enter_for_panic SYM_FUNC_END(__hyp_do_panic) -- 2.40.1 Amazon Web Services Development Center Germany GmbH Krausenstr. 38 10117 Berlin Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss Eingetragen am Amtsgericht Charlottenburg unter HRB 257764 B Sitz: Berlin Ust-ID: DE 365 538 597
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