linux-kernel - [PATCH] KVM: x86/xen: Make number of event channels defines less magical

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Date:   Mon, 14 Nov 2022 18:16:32 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        David Woodhouse <dwmw2@...radead.org>,
        Paul Durrant <paul@....org>
Subject: [PATCH] KVM: x86/xen: Make number of event channels defines less magical

Use BITS_PER_BYTE and sizeof_field() to compute the number of Xen event
channels.  The compat version at least uses sizeof_field(), but the
regular version open codes sizeof_field(), BITS_PER_BYTE, and combines
literals in the process, which makes it far too difficult to understand
relatively straightforward code.

No functional change intended.

Cc: David Woodhouse <dwmw2@...radead.org>
Cc: Paul Durrant <paul@....org>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/xen.h                    | 8 +++++---
 include/xen/interface/event_channel.h | 6 ++++--
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/xen.h b/arch/x86/kvm/xen.h
index 532a535a9e99..c771fbed7058 100644
--- a/arch/x86/kvm/xen.h
+++ b/arch/x86/kvm/xen.h
@@ -9,6 +9,8 @@
 #ifndef __ARCH_X86_KVM_XEN_H__
 #define __ARCH_X86_KVM_XEN_H__
 
+#include <linux/bits.h>
+
 #ifdef CONFIG_KVM_XEN
 #include <linux/jump_label_ratelimit.h>
 
@@ -198,9 +200,9 @@ struct compat_shared_info {
 	struct compat_arch_shared_info arch;
 };
 
-#define COMPAT_EVTCHN_2L_NR_CHANNELS (8 *				\
-				      sizeof_field(struct compat_shared_info, \
-						   evtchn_pending))
+#define COMPAT_EVTCHN_2L_NR_CHANNELS	\
+	 (sizeof_field(struct compat_shared_info, evtchn_pending) * BITS_PER_BYTE)
+
 struct compat_vcpu_runstate_info {
     int state;
     uint64_t state_entry_time;
diff --git a/include/xen/interface/event_channel.h b/include/xen/interface/event_channel.h
index 5f8da466e8a9..c7b97c206226 100644
--- a/include/xen/interface/event_channel.h
+++ b/include/xen/interface/event_channel.h
@@ -10,6 +10,8 @@
 #ifndef __XEN_PUBLIC_EVENT_CHANNEL_H__
 #define __XEN_PUBLIC_EVENT_CHANNEL_H__
 
+#include <linux/bits.h>
+
 #include <xen/interface/xen.h>
 
 typedef uint32_t evtchn_port_t;
@@ -244,8 +246,8 @@ DEFINE_GUEST_HANDLE_STRUCT(evtchn_op);
 /*
  * 2-level ABI
  */
-
-#define EVTCHN_2L_NR_CHANNELS (sizeof(xen_ulong_t) * sizeof(xen_ulong_t) * 64)
+#define EVTCHN_2L_NR_CHANNELS	\
+	 (sizeof_field(struct shared_info, evtchn_pending) * BITS_PER_BYTE)
 
 /*
  * FIFO ABI

base-commit: d663b8a285986072428a6a145e5994bc275df994
-- 
2.38.1.431.g37b22c650d-goog