| Message ID | 20221102231911.3107438-18-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: Rework kvm_init() and hardware enabling | expand |
Hi Sean, On 3/11/22 00:18, Sean Christopherson wrote: > Move arm/arch specific initialization directly in arm's module_init(), > now called kvm_arm_init(), instead of bouncing through kvm_init() to > reach kvm_arch_init(). Invoking kvm_arch_init() is the very first action > performed by kvm_init(), i.e. this is a glorified nop. > > Making kvm_arch_init() a nop will allow dropping it entirely once all > other architectures follow suit. > > No functional change intended. > > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- > arch/arm64/kvm/arm.c | 25 ++++++++++++++++--------- > 1 file changed, 16 insertions(+), 9 deletions(-) > /* NOP: Compiling as a module not supported */ > void kvm_arch_exit(void) > { > - kvm_unregister_perf_callbacks(); Doesn't this belong to the previous patch? > + > }
On Thu, Nov 03, 2022, Philippe Mathieu-Daudé wrote: > Hi Sean, > > On 3/11/22 00:18, Sean Christopherson wrote: > > Move arm/arch specific initialization directly in arm's module_init(), > > now called kvm_arm_init(), instead of bouncing through kvm_init() to > > reach kvm_arch_init(). Invoking kvm_arch_init() is the very first action > > performed by kvm_init(), i.e. this is a glorified nop. > > > > Making kvm_arch_init() a nop will allow dropping it entirely once all > > other architectures follow suit. > > > > No functional change intended. > > > > Signed-off-by: Sean Christopherson <seanjc@google.com> > > --- > > arch/arm64/kvm/arm.c | 25 ++++++++++++++++--------- > > 1 file changed, 16 insertions(+), 9 deletions(-) > > > /* NOP: Compiling as a module not supported */ > > void kvm_arch_exit(void) > > { > > - kvm_unregister_perf_callbacks(); > > Doesn't this belong to the previous patch? No, but the above changelog is a lie, there is very much a functional change here. The goal of the previous patch is to fix the error paths in kvm_arch_init(), a.k.a. kvm_arm_init(). After fixing kvm_arch_init(), there are still bugs in the sequence as a whole because kvm_arch_exit() doesn't unwind other state, e.g. kvm_arch_exit() should really look something like: void kvm_arch_exit(void) { teardown_subsystems(); if (!is_kernel_in_hyp_mode()) teardown_hyp_mode(); kvm_arm_vmid_alloc_free(); if (is_protected_kvm_enabled()) ??? } Becuase although the comment "NOP: Compiling as a module not supported" is correct about KVM ARM always having to be built into the kernel, kvm_arch_exit() can still be called if a later stage of kvm_init() fails. But rather than add a patch to fix kvm_arch_exit(), I chose to fix the bug by moving code out of kvm_arch_init() so that the unwind sequence established in the previous patch could be reused. Except I managed to forget those details when writing the changelog. The changelog should instead be: KVM: arm64: Do arm/arch initialization without bouncing through kvm_init() Do arm/arch specific initialization directly in arm's module_init(), now called kvm_arm_init(), instead of bouncing through kvm_init() to reach kvm_arch_init(). Invoking kvm_arch_init() is the very first action performed by kvm_init(), so from a initialization perspective this is a glorified nop. Avoiding kvm_arch_init() also fixes a mostly benign bug as kvm_arch_exit() doesn't properly unwind if a later stage of kvm_init() fails. While the soon-to-be-deleted comment about compiling as a module being unsupported is correct, kvm_arch_exit() can still be called by kvm_init() if any step after the call to kvm_arch_init() succeeds. Add a FIXME to call out that pKVM initialization isn't unwound if kvm_init() fails, which is a pre-existing problem inherited from kvm_arch_exit(). Making kvm_arch_init() a nop will also allow dropping kvm_arch_init() and kvm_arch_exit() entirely once all other architectures follow suit.
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index f400a8c029dd..bfa2dcd3db11 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -2190,7 +2190,7 @@ void kvm_arch_irq_bypass_start(struct irq_bypass_consumer *cons) /** * Initialize Hyp-mode and memory mappings on all CPUs. */ -int kvm_arch_init(void *opaque) +int kvm_arm_init(void) { int err; bool in_hyp_mode; @@ -2264,6 +2264,14 @@ int kvm_arch_init(void *opaque) kvm_info("Hyp mode initialized successfully\n"); } + /* + * FIXME: Do something reasonable if kvm_init() fails after pKVM + * hypervisor protection is finalized. + */ + err = kvm_init(NULL, sizeof(struct kvm_vcpu), 0, THIS_MODULE); + if (err) + goto out_subs; + return 0; out_subs: @@ -2276,10 +2284,15 @@ int kvm_arch_init(void *opaque) return err; } +int kvm_arch_init(void *opaque) +{ + return 0; +} + /* NOP: Compiling as a module not supported */ void kvm_arch_exit(void) { - kvm_unregister_perf_callbacks(); + } static int __init early_kvm_mode_cfg(char *arg) @@ -2320,10 +2333,4 @@ enum kvm_mode kvm_get_mode(void) return kvm_mode; } -static int arm_init(void) -{ - int rc = kvm_init(NULL, sizeof(struct kvm_vcpu), 0, THIS_MODULE); - return rc; -} - -module_init(arm_init); +module_init(kvm_arm_init);
Move arm/arch specific initialization directly in arm's module_init(), now called kvm_arm_init(), instead of bouncing through kvm_init() to reach kvm_arch_init(). Invoking kvm_arch_init() is the very first action performed by kvm_init(), i.e. this is a glorified nop. Making kvm_arch_init() a nop will allow dropping it entirely once all other architectures follow suit. No functional change intended. Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/arm64/kvm/arm.c | 25 ++++++++++++++++--------- 1 file changed, 16 insertions(+), 9 deletions(-)