diff options
Diffstat (limited to '0043-x86-altp2m-help-gcc13-to-avoid-it-emitting-a-warning.patch')
| -rw-r--r-- | 0043-x86-altp2m-help-gcc13-to-avoid-it-emitting-a-warning.patch | 129 |
1 files changed, 129 insertions, 0 deletions
diff --git a/0043-x86-altp2m-help-gcc13-to-avoid-it-emitting-a-warning.patch b/0043-x86-altp2m-help-gcc13-to-avoid-it-emitting-a-warning.patch new file mode 100644 index 0000000..0e040ad --- /dev/null +++ b/0043-x86-altp2m-help-gcc13-to-avoid-it-emitting-a-warning.patch @@ -0,0 +1,129 @@ +From cdde3171a2a932a6836b094c4387412e27414ec9 Mon Sep 17 00:00:00 2001 +From: Jan Beulich <jbeulich@suse.com> +Date: Tue, 21 Mar 2023 13:51:42 +0100 +Subject: [PATCH 43/61] x86/altp2m: help gcc13 to avoid it emitting a warning + +Switches of altp2m-s always expect a valid altp2m to be in place (and +indeed altp2m_vcpu_initialise() sets the active one to be at index 0). +The compiler, however, cannot know that, and hence it cannot eliminate +p2m_get_altp2m()'s case of returnin (literal) NULL. If then the compiler +decides to special case that code path in the caller, the dereference in +instances of + + atomic_dec(&p2m_get_altp2m(v)->active_vcpus); + +can, to the code generator, appear to be NULL dereferences, leading to + +In function 'atomic_dec', + inlined from '...' at ...: +./arch/x86/include/asm/atomic.h:182:5: error: array subscript 0 is outside array bounds of 'int[0]' [-Werror=array-bounds=] + +Aid the compiler by adding a BUG_ON() checking the return value of the +problematic p2m_get_altp2m(). Since with the use of the local variable +the 2nd p2m_get_altp2m() each will look questionable at the first glance +(Why is the local variable not used here?), open-code the only relevant +piece of p2m_get_altp2m() there. + +To avoid repeatedly doing these transformations, and also to limit how +"bad" the open-coding really is, convert the entire operation to an +inline helper, used by all three instances (and accepting the redundant +BUG_ON(idx >= MAX_ALTP2M) in two of the three cases). + +Reported-by: Charles Arnold <carnold@suse.com> +Signed-off-by: Jan Beulich <jbeulich@suse.com> +Acked-by: Andrew Cooper <andrew.cooper3@citrix.com> +master commit: be62b1fc2aa7375d553603fca07299da765a89fe +master date: 2023-03-13 15:16:21 +0100 +--- + xen/arch/x86/hvm/vmx/vmx.c | 8 +------- + xen/arch/x86/mm/p2m.c | 14 ++------------ + xen/include/asm-x86/p2m.h | 20 ++++++++++++++++++++ + 3 files changed, 23 insertions(+), 19 deletions(-) + +diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c +index 094141be9a..c8a839cd5e 100644 +--- a/xen/arch/x86/hvm/vmx/vmx.c ++++ b/xen/arch/x86/hvm/vmx/vmx.c +@@ -4036,13 +4036,7 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs) + } + } + +- if ( idx != vcpu_altp2m(v).p2midx ) +- { +- BUG_ON(idx >= MAX_ALTP2M); +- atomic_dec(&p2m_get_altp2m(v)->active_vcpus); +- vcpu_altp2m(v).p2midx = idx; +- atomic_inc(&p2m_get_altp2m(v)->active_vcpus); +- } ++ p2m_set_altp2m(v, idx); + } + + /* XXX: This looks ugly, but we need a mechanism to ensure +diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c +index 8781df9dda..2d41446a69 100644 +--- a/xen/arch/x86/mm/p2m.c ++++ b/xen/arch/x86/mm/p2m.c +@@ -2194,13 +2194,8 @@ bool_t p2m_switch_vcpu_altp2m_by_id(struct vcpu *v, unsigned int idx) + + if ( d->arch.altp2m_eptp[idx] != mfn_x(INVALID_MFN) ) + { +- if ( idx != vcpu_altp2m(v).p2midx ) +- { +- atomic_dec(&p2m_get_altp2m(v)->active_vcpus); +- vcpu_altp2m(v).p2midx = idx; +- atomic_inc(&p2m_get_altp2m(v)->active_vcpus); ++ if ( p2m_set_altp2m(v, idx) ) + altp2m_vcpu_update_p2m(v); +- } + rc = 1; + } + +@@ -2471,13 +2466,8 @@ int p2m_switch_domain_altp2m_by_id(struct domain *d, unsigned int idx) + if ( d->arch.altp2m_visible_eptp[idx] != mfn_x(INVALID_MFN) ) + { + for_each_vcpu( d, v ) +- if ( idx != vcpu_altp2m(v).p2midx ) +- { +- atomic_dec(&p2m_get_altp2m(v)->active_vcpus); +- vcpu_altp2m(v).p2midx = idx; +- atomic_inc(&p2m_get_altp2m(v)->active_vcpus); ++ if ( p2m_set_altp2m(v, idx) ) + altp2m_vcpu_update_p2m(v); +- } + + rc = 0; + } +diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h +index 2db9ab0122..f92bb97394 100644 +--- a/xen/include/asm-x86/p2m.h ++++ b/xen/include/asm-x86/p2m.h +@@ -841,6 +841,26 @@ static inline struct p2m_domain *p2m_get_altp2m(struct vcpu *v) + return v->domain->arch.altp2m_p2m[index]; + } + ++/* set current alternate p2m table */ ++static inline bool p2m_set_altp2m(struct vcpu *v, unsigned int idx) ++{ ++ struct p2m_domain *orig; ++ ++ BUG_ON(idx >= MAX_ALTP2M); ++ ++ if ( idx == vcpu_altp2m(v).p2midx ) ++ return false; ++ ++ orig = p2m_get_altp2m(v); ++ BUG_ON(!orig); ++ atomic_dec(&orig->active_vcpus); ++ ++ vcpu_altp2m(v).p2midx = idx; ++ atomic_inc(&v->domain->arch.altp2m_p2m[idx]->active_vcpus); ++ ++ return true; ++} ++ + /* Switch alternate p2m for a single vcpu */ + bool_t p2m_switch_vcpu_altp2m_by_id(struct vcpu *v, unsigned int idx); + +-- +2.40.0 + |