Messages in this thread | | | Date | Thu, 3 Nov 2022 15:29:58 +0000 | From | Sean Christopherson <> | Subject | Re: [PATCH 17/44] KVM: arm64: Do arm/arch initialiation without bouncing through kvm_init() |
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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.
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