On 29.06.26 08:52, Arnd Bergmann wrote:
On Mon, Jun 29, 2026, at 08:04, Juergen Gross wrote:For accessing the MSR registers on the local CPU, there are 2 types of interfaces: the "modern" 64-bit ones (rdmsrq() etc.) and the 32-bit ones (rdmsr() etc.) which are using the upper and lower 32-bit halves of the 64-bit wide MSR register values.The 32-bit interfaces are not optimal for 3 reasons: - They are based on primitives using 64-bit sized values anyway. - Modern x86 CPUs have added support for MSR access instructions using an immediate value instead of a register for addressing the MSR, while the value is in a 64-bit register. - rdmsr() is a macro storing the upper and lower 32-bit halves in variables specified as macro parameters. This is obscuring variable assignment through a macro. Additionally rdmsrq() is mimicking this pattern by being a macro, too, with the target variable specified as a parameter as well. For those reasons drop the 32-bit interfaces for accessing the x86 MSR registers completely and only use the 64-bit variants.Hi Jürgen, I assume this is fine, but since you don't mention it explicitly here, please clarify what this means for 32-bit CPUs without the rdmsrq instruction. Those will continue using the same instructions as before and just change the calling conventions, right?
Yes. I thought this would be clear from the following: - They are based on primitives using 64-bit sized values anyway.
Note that most patches of this series are independent from each other. Only the patches removing a specific interface (patches 7, 15, 26 and 30) and the last two patches of the series depend on all previous patches.It looks like you are touching most files twice or more here, to first convert from rdmsr to rdmsrq and then to change the two-argument rdmsrq() macro to a single-argument inline. If you introduce the inline version of rdmsrq() first, you should be able to skip the second step (patch 31) as they could be able to coexist.
I've discussed how to structure the series with Ingo Molnar before [1]. The current approach was his preference. Juergen [1]: https://lore.kernel.org/lkml/[email protected]/
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