Re: [PATCH] passing smp cpu count from CMOS

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

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He, Qing wrote:
> As discussed previously, this patch directly passes SMP CPU count to the
> guest BIOS from CMOS by qemu, instead of sending SIPI and wait. CMOS
> offset 0x7f is used.
>
> This is the last functional piece for in-kernel APIC merge in kvm-37.
>
> Signed-off-by: Qing He <qing.he-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> diff --git a/bios/rombios32.c b/bios/rombios32.c
> index faf771e..3bb5e00 100755
> --- a/bios/rombios32.c
> +++ b/bios/rombios32.c
> @@ -41,6 +41,9 @@ typedef unsigned long long uint64_t;
>  /* define it if the (emulated) hardware supports SMM mode */
>  #define BX_USE_SMM
>  
> +/* read CPU count from CMOS directly instead of probing */
> +#define BX_CMOS_CPU_COUNT
> +
>  #define cpuid(index, eax, ebx, ecx, edx) \
>    asm volatile ("cpuid" \
>                  : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx) \
> @@ -442,9 +445,13 @@ void smp_probe(void)
>          sipi_vector = AP_BOOT_ADDR >> 12;
>          writel(APIC_BASE + APIC_ICR_LOW, 0x000C4600 | sipi_vector);
>          
> +#ifdef BX_CMOS_CPU_COUNT
> +        smp_cpus = cmos_readb(0x7f);
> +#else
>          delay_ms(10);
>  
>          smp_cpus = readw((void *)CPU_COUNT_ADDR);
> +#endif
>   

This means there's no BIOS SIPI, which is a little sad as it doesn't 
exercise the lapic machinery.

> diff --git a/qemu/hw/mc146818rtc.c b/qemu/hw/mc146818rtc.c
> index bad4cbd..3c4c25d 100644
> --- a/qemu/hw/mc146818rtc.c
> +++ b/qemu/hw/mc146818rtc.c
> @@ -33,6 +33,9 @@
>  #define RTC_HOURS_ALARM         5
>  #define RTC_ALARM_DONT_CARE    0xC0
>  
> +/* KVM specific extension: smp cpu count passing */
> +#define RTC_CMOS_CPU_COUNT     0x7f
> +
>  #define RTC_DAY_OF_WEEK         6
>  #define RTC_DAY_OF_MONTH        7
>  #define RTC_MONTH               8
> @@ -356,6 +359,9 @@ static uint32_t cmos_ioport_read(void *opaque,
> uint32_t addr)
>              pic_set_irq(s->irq, 0);
>              s->cmos_data[RTC_REG_C] = 0x00; 
>              break;
> +        case RTC_CMOS_CPU_COUNT:
> +            ret = smp_cpus;
> +            break;
>   

This really shouldn't be done from within the rtc.

Alternative patch attached, but works only with -no-kvm-irqchip.


-- 
error compiling committee.c: too many arguments to function


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diff --git a/bios/BIOS-bochs-latest b/bios/BIOS-bochs-latest
index 4388ff2..c10ae62 100644
Binary files a/bios/BIOS-bochs-latest and b/bios/BIOS-bochs-latest differ
diff --git a/bios/BIOS-bochs-legacy b/bios/BIOS-bochs-legacy
index a720312..131e62b 100644
Binary files a/bios/BIOS-bochs-legacy and b/bios/BIOS-bochs-legacy differ
diff --git a/bios/rombios32.c b/bios/rombios32.c
index 816e5cc..1917b1c 100755
--- a/bios/rombios32.c
+++ b/bios/rombios32.c
@@ -441,7 +441,12 @@ void smp_probe(void)
         sipi_vector = AP_BOOT_ADDR >> 12;
         writel(APIC_BASE + APIC_ICR_LOW, 0x000C4600 | sipi_vector);
         
+#ifndef BX_QEMU
         delay_ms(10);
+#else
+	while (cmos_readb(0x5f) + 1 != readw((void *)CPU_COUNT_ADDR))
+	    ;
+#endif
 
         smp_cpus = readw((void *)CPU_COUNT_ADDR);
     }
diff --git a/qemu/hw/pc.c b/qemu/hw/pc.c
index d3b8786..7c6ceb1 100644
--- a/qemu/hw/pc.c
+++ b/qemu/hw/pc.c
@@ -163,7 +163,7 @@ static void cmos_init_hd(int type_ofs, int info_ofs, BlockDriverState *hd)
 }
 
 /* hd_table must contain 4 block drivers */
-static void cmos_init(ram_addr_t ram_size, ram_addr_t above_4g_mem_size, int boot_device, BlockDriverState **hd_table)
+static void cmos_init(ram_addr_t ram_size, ram_addr_t above_4g_mem_size, int boot_device, BlockDriverState **hd_table, int smp_cpus)
 {
     RTCState *s = rtc_state;
     int val;
@@ -190,6 +190,7 @@ static void cmos_init(ram_addr_t ram_size, ram_addr_t above_4g_mem_size, int boo
         rtc_set_memory(s, 0x5c, (unsigned int)above_4g_mem_size >> 24);
         rtc_set_memory(s, 0x5d, above_4g_mem_size >> 32);
     }
+    rtc_set_memory(s, 0x5f, smp_cpus - 1);
 
     if (ram_size > (16 * 1024 * 1024))
         val = (ram_size / 65536) - ((16 * 1024 * 1024) / 65536);
@@ -778,7 +779,7 @@ static void pc_init1(ram_addr_t ram_size, int vga_ram_size, int boot_device,
 
     floppy_controller = fdctrl_init(6, 2, 0, 0x3f0, fd_table);
 
-    cmos_init(ram_size, above_4g_mem_size, boot_device, bs_table);
+    cmos_init(ram_size, above_4g_mem_size, boot_device, bs_table, smp_cpus);
 
     if (pci_enabled && usb_enabled) {
         usb_uhci_init(pci_bus, piix3_devfn + 2);
diff --git a/qemu/pc-bios/bios.bin b/qemu/pc-bios/bios.bin
index 4388ff2..c10ae62 100644
Binary files a/qemu/pc-bios/bios.bin and b/qemu/pc-bios/bios.bin differ

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